Im a 15 yr old, 5ft 103lbs female. My bmr is approx. 1200. I work out everyday - my workouts equaling 1300-1400 burn a day. Coupled with my bmr, that's 2500-2600 burned each day. I usually only eat a total of 1800cal. I haven't lost weight-in fact, I've gained some. Im wondering if I'm slowing my metabolism by eating less than my bmr. If so, should I eat back my work out cal in order to equal my bmr? Will this help me lose weight?

You are probably converting some fat to muscle. Muscle is more dense. Why do you want to lose weight? BMI chart shows your weight range for your height is 97-123-sounds like you are perfect!

Well.. I want to be thin. Like in the real low side of my weight class. I know it's silly but my weight kind of defines my mood, which is bad but its really too late for me to change.

You are only 15. It's not too late to change. These thoughts are unhealthy and borderline anorexic. You need to seek counseling before this gets out of hand.