Are you kidding me?!

Check out the blog I wrote yesterday about this issue. given that you are not too far from a healthy weight.

http://www.myfitnesspal.com/blog/00trayn/view/how-to-bust-a-3-month-plateau-87677

When you become active and exercise with both resistance training and cardio body WEIGHT becomes a much poorer guage of overall fitness. Unfortunately this includes Body Mass Index (BMI), which is only designed to account for weight and height. Circumference Measurements and estimated percent body fat are much more useful tools )

I didn't lose anything for close to 3 weeks, I even gained 2 lbs. the first few days. Sometimes the body goes into shock and the change of plans and takes a while to adjust. Another thing is that you only have 18 lbs. to lose and several of the more seasoned MFP'ers would say trying to lose 2 lbs. a week with so little to lose is part of the issue. If you haven't already done it, make your food diary public so people can take a look and see if there is something you are missing. Also mention what kind of exercise and how often you are exercising.

Don't give up it's a process and sometimes a slow one!

you could also be eating too little.. eat back your exercise cals too. With such little weight to lose, it comes off slower and should be done more slowly.

Are you sure your calories aren't set too low? 1200 seems very little if you have 18 lbs to lose to get to a healthy BMI. I eat more than that, and my BMI is 24.

Maybe your target weight loss should be adjusted, you might have it at "lose 2 lbs a week", but I'd go for a lower target, 1 or even 1/2 lbs a week. I know it sounds mad to eat more to lose more but there's various threads on this subject and it actually does work.

Are you sure your calories aren't set too low? 1200 seems very little if you have 18 lbs to lose to get to a healthy BMI. I eat more than that, and my BMI is 24.

Maybe your target weight loss should be adjusted, you might have it at "lose 2 lbs a week", but I'd go for a lower target, 1 or even 1/2 lbs a week. I know it sounds mad to eat more to lose more but there's various threads on this subject and it actually does work.

yes check your goals. I had 10 pounds to lose (in the upper range of healthy). The only choice I had was .5 per week (too few calories can affect weight loss especially if your exercising). I saw loss in .2-.4lb increments (and lost 2 pounds after upping my calories to maintenance).

I have been training for a half marathon, running about 70-80 mins 3-4 x a week, I have done circuit training 2-3x week of push ups, squats etc..and I typically do a brisk walk during my breaks at work for about 30-40 mins a day too...I dont know why I am so focused on the weight, I know alot of factors go into it... but its frustrating to me. Thanks!

you could be exercising too much.

The law of unintended consequences

Your body is an amazing feedback system aimed at balance and survival. Humans are at the top of the food chain because they are able to adapt to their environment. Every action produces a reaction. Every change in its environment triggers a survival response. It's important to keep that in mind when you plan your fitness program. If you treat your body as an enemy to be conquered, you'll produce unintended results.

For example, if you severely cut off the supply of food to your body, it will defend itself by slowing down its metabolism to survive starvation. The body will shed muscle mass the same way that you would throw cargo from a plane that was low on fuel, and it will reduce its thyroid activity to conserve energy. The body will also actually defend its fat stores. In anorexia, muscle loss can be so profound that fat as a percentage of body weight actually rises. Extreme carbohydrate restriction also causes muscle loss, dehydration, and slower metabolism, which is why even successful Atkins dieters can have a significant rebound in weight after they stop the diet (don't worry – the advice on this site will prevent that from happening).

As another example, if you put your body under stress through overexertion and lack of sleep, it will respond by slowing down, reducing muscle growth, and increasing your appetite for junk food, carbohydrates and fat. If you feed your body excessive amounts of sugar and quickly digested carbohydrates, and it will shut off its ability to burn fat until those sugars are taken out of the bloodstream.

This website will show you how to work with your body to quickly produce the changes you want. In order to do that, you need to take actions that push your body to adapt – to build strength, burn fat, and increase fitness. You need a training program, not an exercise routine. You need a nutrition plan, not a diet. You need a challenge, not a few good habits you usually try to follow except when you don't.
Setting the right goal

John Dewey once said that a problem well-stated is half-solved. If you want to reach your goal, you have to define it correctly. See, a lot of people say “I want to lose weight.” Well, if losing weight is your goal, go on a no-carb diet. You'll lose a lot of weight – some of it will be fat, a lot of it will be water, and a dangerous amount will be muscle tissue. You'll lose weight quickly, but you'll slow your metabolism and gain fat more quickly once you go off the diet. Trust me on this. I've been there, done that.

The problem is that you've set the wrong goal. If you want to look better, have more energy and enjoy better health, the goal is not simply to “lose weight.” The goal is to improve your fitness level and body composition. That means losing fat, improving your aerobic capacity, training your strength and defending your muscle tissue. You can't do that with a no-carb diet. You will do it using the approach you'll learn on this website. Trust me on this one too. I know what it's like to feel fat, tired and helplessly out of shape. The whole point of this site is to help others avoid that, by sharing lessons that I had to learn the hard way.

http://www.hussmanfitness.org/html/TPAdaptation.html (ignore that it is focusing towards no-carbers and low-carbers. )

Too much cardio can also keep you from losing even with strength training. You end up losing too much muscle mass and your metabolism slows. (Overexertion). With that much exercise I would be eating way over 1200 and eating back exercise calories (but that is just me.)