I'm really tired?

Eat more. As long as you're eating at a deficit, you will lose weight.

Think of it this way. If you're getting lethargic, you're going to move less and sleep more. When this happens, you're going to be expending even less energy (burning calories) through normal movement. If you eat a bit more, you'll feel better and you'll move more. Thus, you'll be happier eating more, moving more and still losing weight.

You'll lose steadily and in a healthy way if you fuel your body properly. 1200 calories/day may not be enough for you if you're feeling tired after 3 days.
What are your goal settings? 2 lbs a week? Perhaps try 1 lb a week for awhile and see if that keeps you feeling more energized.
It's better to lose slowly and be able to stick to a new lifestyle than lose quickly and give up.
Also, reach your calorie intake daily (or very close to it). Having 500 or so calories left means you need to eat more.
If you're using MFP's calories for exercise, it's best to only "eat back" half or three quarters of them. MFP tends to be high on the calorie burns.

Hang in there. Eat enough to fuel your body. Learn a new lifestyle that you can maintain throughout life. You'll do well. Take it slow.

I took a look at your macros and your caloric intake for the day and based on your body weight, you're eating WAY too little for your body.You're going to feel lightheaded, have no energy, be generally cranky, and probably not be able to keep this way of eating up before you burn out and get frustrated. You're also eating a lot of sugar and processed food. Try and slowly move toward more whole foods and stay away from prepackaged stuff. If it comes in a wrapper and is made in a factory then it's not food.

My advice is to find out what your TDEE is and use that as your base caloric intake. Without knowing what your height is, just your age and weight and assuming you're around 5'6", you should be eating closer to ~1800 calories per day. Macronutrient numbers (thanks to Scooby's calculator) need to be closer to 200g of protein, 84g of carbohydrates and 56g of fat per day.

Chicken, fish, turkey, beef, all provide protein. More protein/fat will help keep you feeling full for longer. Do you have a digital food scale? If you don't, go buy one. Here's one on Amazon for around 16 bucks. Consider it an investment in your health for the future. http://amzn.to/1tcA0m3 Weigh all of your foods and keep a log of what you're putting into your mouth EVERY DAY for two weeks. Be honest with yourself.

You're going to have to start pre-planning meals instead of rummaging through the fridge and hoping you're making good choices. Make a grocery list or a meal plan and stick to it. My girlfriend and I go shopping every Sunday. (She was around your weight when she started losing about a year ago and has lost ~65lbs on ~1650 calories per day) We make our lunch the night before we go to work.

If you're not ready for that kind of commitment, you can always use a palm-sized portion of protein (lean beef, chicken, fish, etc) or a portion about the size of a deck of cards, a fist sized portion of carbohydrates (brown rice, whole wheat bread, etc) and as many vegetables as you would like to eat (except for corn) as long as they are not slathered with sauce. Eat 4-6 times a day if it helps or less if you would like to eat bigger meals. Whatever works best for your lifestyle.

Either way, 1200 cals is too low for a person of your size. You're not going to make much progress at that level unless you have the willpower of a Guantanamo detainee. Even if you do, you're going to feel like **** throughout the whole process.

I took a look at your macros and your caloric intake for the day and based on your body weight, you're eating WAY too little for your body.You're going to feel lightheaded, have no energy, be generally cranky, and probably not be able to keep this way of eating up before you burn out and get frustrated. You're also eating a lot of sugar and processed food. Try and slowly move toward more whole foods and stay away from prepackaged stuff. If it comes in a wrapper and is made in a factory then it's not food.

My advice is to find out what your TDEE is and use that as your base caloric intake. Without knowing what your height is, just your age and weight and assuming you're around 5'6", you should be eating closer to ~1800 calories per day. Macronutrient numbers (thanks to Scooby's calculator) need to be closer to 200g of protein, 84g of carbohydrates and 56g of fat per day.

Chicken, fish, turkey, beef, all provide protein. More protein/fat will help keep you feeling full for longer. Do you have a digital food scale? If you don't, go buy one. Here's one on Amazon for around 16 bucks. Consider it an investment in your health for the future. http://amzn.to/1tcA0m3 Weigh all of your foods and keep a log of what you're putting into your mouth EVERY DAY for two weeks. Be honest with yourself.

You're going to have to start pre-planning meals instead of rummaging through the fridge and hoping you're making good choices. Make a grocery list or a meal plan and stick to it. My girlfriend and I go shopping every Sunday. (She was around your weight when she started losing about a year ago and has lost ~65lbs on ~1650 calories per day) We make our lunch the night before we go to work.

If you're not ready for that kind of commitment, you can always use a palm-sized portion of protein (lean beef, chicken, fish, etc) or a portion about the size of a deck of cards, a fist sized portion of carbohydrates (brown rice, whole wheat bread, etc) and as many vegetables as you would like to eat (except for corn) as long as they are not slathered with sauce. Eat 4-6 times a day if it helps or less if you would like to eat bigger meals. Whatever works best for your lifestyle.

Either way, 1200 cals is too low for a person of your size. You're not going to make much progress at that level unless you have the willpower of a Guantanamo detainee. Even if you do, you're going to feel like **** throughout the whole process.

Yes, OP, you should eat more whole foods, pay attention to getting more protein and up your calories.

Per bolded, no, even food in packages is still food.

I'm only 5'2'', quite small.

And I know I should be eating whole foods, but I don't buy groceries and we have a very low budget to work with. My boyfriend and I only have about 700 a month for rent and food, and he's a pescatarian, so tuna is pretty much the only meat I can eat. I know you are totally 100% right, I just don't have any idea how I can afford to be buying meat and anything other than frozen vegetables, as anything spoiled is a complete waste.

I know that it's not much of an excuse, but it's what I feel like I can do right now.

There's nothing wrong with frozen vegetables. You can also buy chicken in bulk, add it to frozen stir fry veggies and have a great protein/veggie meal. You can add the chicken at the end to only your portion that way your BF can keep to his pescatarian ways and you can get more protein. You can also grill/bake several pieces of chicken in advance and eat them with your lunches over the next several days.

Google TDEE, calculate, don't starve, that is all.

Rigger

So the calculator tells me that my BMR is 1787 and my TDEE is 2145.

So I shouldn't be eating 1200 cals a day, but at LEAST 1787? Is that how this is supposed to work? Wouldn't I lose slower, or does my body think I'm dying at 1200 cals a day?

I'm so hopeless at this lol

::pat pat pat:: It's okay grasshopper, we'll walk you through it. Everyone starts somewhere. :-)

Yes, eat more food, the BMR thing is not really a hard and fast rule (though there are people who will disagree), but I'd say 1700-1800 is a GREAT place to be working from at your phase. I'm taller than you (5' 7") and I eat about 1900.

Here are some good budget-friendly ideas.

1. You say you're eating tuna and want to stick to cheap fishy meats because of boyfriends's pesco-ness. You can also get (very cheap!) canned salmon for a comparable price. My grocery store sells Chicken of the Sea pink salmon in foil packets for about the same price as tuna. Also, consider sardines. I like them with lemon pasta and broccoli for a super-cheap healthy meal.

2. Eggs. Don't know if the boyfriend eats those, but if not they can be just for you. About the cheapest protein available LOL. Even if you throw the yolks out to avoid fats (protip: you don't need to do that but some people do, whatever) they're still insanely cheap.

3. Dairy. If you and/or boyfriend can/ do eat dairy, milk can be a great diet food. I drink 12 oz every day to help meet my protein goals, and also because mmmm, delicious milk. Lately I've been blending my milk with a couple of cups of strawberries for strawberry milk (and frozen strawberries work great for that too). Yogurt can be cheap as well -- I get the store-brand plain greek kind and I'm very happy with it. I mostly blend it with a little milk and cinnamon and soak oatmeal in it overnight, but I also like adding it at the end for vegetable or meat curry dishes.

4. Carbs. Okay, carbs are "controversial" because some dieters here are low-carb fanatics (protip: very few medical professionals agree with extreme low-carbism for most patients and generally advocate moderate carbs from sensible foods), and someone here will probably yell at me for promoting them. But if you're actually feeling lethargic, getting some sensible carbs in is the best way to keep that at bay. I eat a moderate level of carbs in my diet (about 200 g / day or <45% of my calories). I mysteriously felt like crap on a cracker all day yesterday. Finally investigated my diary and realized that I only at like 1/4 of my daily usual carbs until like 10pm, and I worked out (HARD) twice yesterday. So I think I was almost bonked. Carbs are cheap! Whole wheat pasta is super budget friendly. Also, beans -- they are not only a FANTASTIC source of healthy low-glycemic carbs but also fiber and a non-trivial amount of protein. If you don't eat beans already (or if you don't think you like them), try frozen edamame: they're not terribly beany. But canned beans are great budget food, insanely convenient, and a great addition to salads, pastas, soups and stews, stir frys, curries, etc.

Ah, thank you, this is all excellent. I do eat a lot of eggs, they are one of the main ways I get my protein.

I think I'm just looking at it wrong. I thought the point of excersise was to burn even more calories, but the internet and all you people tell me it's more like icing on the cake that makes you more fit. ^^

When I started last year that's what I thought too. With the corollary that exercise also makes it possible to keep a target deficit while eating a more enjoyable, varied diet (i.e., moar food). When you have a lot of weight to lose, making sure that your diet deficit is a number that you can actually LIVE WITH for a long time without feeling deprived or resentful or desperate is a big key to success. I would not have lasted this long without being able to incorporate small portions of treats like chocolate or peanut butter or booze now and then. I never "cheat": I can make anything fit the plan with a little work. Christmas and Thanksgiving were no problem.

BUT over time I discovered with the exercise that I did REALLY like what it was doing for my body. It's not JUST about burning calories (and either losing faster or earning more food)! I feel STRONG, I have a ton of energy, I'm CAPABLE. My flexibility and mobility improved FAST. Running up and down stairs: possible. I'm older than you so this is all more of a re-discovery, like finding a second youth. Not to mention the new hawtness. But watching my health stats improve has also been very gratifying. Off BP meds, check. Resting heart rate in "conditioned athlete" territory: check. Visible muscle tone: check. My whole life I've hated exercise but now I get it: WORTH IT. And after a couple of months, I didn't even hate it anymore.