what's going on???

I am just recently getting over a small eating disorder. I was down to eating less than 1,000 calories a day. My CC calorie intake says that it should be about 1600 to maintain at a sedentary lifestyle. I do work out everyday but I only do like 500 situps and pushups and stuff like that. Since I was only eating like 900 calories a day I only brought my calorie intake up to 1300. But I'm gaining weight at only 1300 and my BMR said that if I laid in bed all day and didn't even move I would burn more calories than that. So what is going on?

 

My Stats:

 Age: 16

Weight: 120ish

Height: 5'4

The BMR you should have may not be the one you do have if you have one of any number of health issues. Also, after you make your body think it is starving by having too few calories, when you do eat properly again your body starts storing up to make up for that period when it thought it was starving.