I work 11 hours a day and I go to school full time. I eat less than I normally eat but I have a 'dunlap'! I don't understand why I'm in a size nine pants from a five just a year ago. Is it because my job is a sit down? Or can it be something worse? I went to the dr a few months ago and she said my tyroid was just a little high but not alarming, under a 1.0. Its upsets me that she doesn't know why such a weight change.

Check with another doctor for hyper thyroidism...
Exercise will definitely help, given that you have a sitting job...
Eat healthy food.

Check with another doctor for hyper thyroidism...

Actually Hyperthyroid would make her lose weight. Not gain.

Now, to the OP....it could be that your metabolism is slowing down if you are not eating that much. When you are busy and not eating your body grabs and holds every calorie you put in your mouth. Therefore, you gain weight while eating little.