Goal calorie intake: 1800... but I usually only get 1200

Well, given that your goal is 1800, then yes, try to eat more.

Well, we don't know your height or current weight, but if MFP tells you to eat 1800 based on the data you input, then you'd better find ways to do that. If you are filling up on "diet" foods, replace some of those with the real thing. Eat an ounce of nuts, have a piece of cheese, throw in a boiled egg or some hummus and pita as a snack. One of my favorite evening snacks if I need more is a whole grain sandwich thin toasted with orange marmalade.

Food is delicious. Plan better and try not to under eat. It will surely backfire.

Something is wrong when you are full from having a half a bell pepper for lunch.

I would try to eat denser foods like - avocado, peanut butter, nuts, eggs, yogurt, etc

^^
On days when I'm eating straight plants and fruits, I find it hard to reach even 1200. Almond butter on bananas and avocados always help me reach 1200 and beyond. Try eating ginger (on foods or in tea) too; its natural heat helps promote appetite.

The question that I would ask is this: what do you plan to do when you reach your goal and transition to maintenance? One of the important advantages to the MFP slow-and-steady method is that you learn a lot of healthy habits that will help you keep the weight off and stay healthy in the future. If you can't eat 1800 calories now, is your maintenance plan to just keep eating 1200 until your metabolism finally slows down enough that you stop losing weight?

I would try to eat denser foods like - avocado, peanut butter, nuts, eggs, yogurt, etc

This. Full fat dairy, cheese, almonds, avocado, peanut butter, nuts, seeds, dark chocolate even.
Or add some snacks between meals.
Just because you feel full, does not mean your body has received adequate nutrition for optimal function.

carbs in the morning? When I have cereal or oatmeal I am usually hungry a couple hours later :ohwell:

I fail to see where carbs in the morning is mentioned in these posts ?

Your profile says you are a recovered anorexic but your diary has some worrying indications of relapse. I would suggest you seek professional and medical assistance rather than getting advice from MFP forums. Take care of your body. It needs nourishment to work properly

ETA: Just to let you know as well, that "feeling full" isn't always the best indicator of what you need. My suggestion is to have very tiny snacks, like five almonds every ten minutes between all meals. It's not going to make you stuffed but it will help you increase calories throughout the day.

ETA: Okay, I've just read through your full diary and I want to reiterate my suggestion that you visit a doctor and a psychologist. Especially if "tea" is just a "snack" then you are missing out dinner altogether. No wonder you aren't meeting calorie requirements with a whole meal not eaten. Good luck.

If you're having trouble getting those calories in, I would suggest high calorie breakfast and snacks. A bowl of oatmeal with some peanut butter, or maybe with apples and walnuts and whey protein powder would be an awesome start and good way to cram in calories. Snacking on dates and walnuts is a favorite of mine, they're so good together and have a ton of calories. It would make a good post workout snack. Get in your healthy fats, olive oil, coconut, avocado, (again) walnuts. Also, whole eggs, cottage cheese with fruit are yummy. My diary is open (and I know we're friends) and you can take a look for some ideas. If I could eat a billion calories a day, I would, lol.

If your goal is not to lose weight, but to tone your body, then you definitely need to be eating more good-fat and protein foods. I assume you are working out, because there's really no way to tone up without exercise. Best thing you can do is find some sort of nuts that you enjoy, and eat a handful or two of those shortly before or shortly after your workout. Say hello to peanut butter again, it can be your friend here. A peanut butter and banana sandwich is highly delicious, highly nutritious, and calorically dense. As some other people have mentioned, avocados are a great food to add to your diet as well. Avoid empty calories if your problem is feeling full - rice isn't particularly nutritious, and does tend to fill you up (although only briefly). The very most important thing is to make sure you're getting enough nutrients in what you eat. If you come in at 1500 or whatever sometimes, but it was all good fats and protein and vitamin-rich foods, you should be okay. Try and hit 1800 as much as you can though, because if you're working out a lot to tone up but not giving your body what it needs in order to maintain itself, it won't work.