Am I Anorexic even though I have an average BMI?

Hi :) I am 16yrs old and 5ft 9, a few months ago I was at 10st 5pounds. That seemed to be my natural weight. Then after a few weeks of going to the gym and not eating very much I got down to 9st 11pounds and am still not happy. I am extremely obsessive about it-I measure my waist every day as I am hoping to reach 24inches (like that of a supermodel) but I am 26 and it doesn't seem to budge. I have a very small lunch at school of about 150kcal probably less because that is when i can control what I eat and do, after that I go to the gym and burn off about 300kcal on average. If I reach 9stone 12 at any point I freak out and immediately try and get back down. During class i sit and watch the time counting how many "stomach vacuums" i can do. It did get to a point where I was in significant pain, after taking in a negative intake of calories (due to a lot of exercise) I curled over on a walk because my insides were that painful. I am more determined than ever to loose more wieght but I don't think this is a natural obsession. I watch an episode of supersize vs superskinny every night and I think the superskinny people are perfect, although the doctors are saying it is not. I have a BMI at the moment of 20 and still feel fat. I think I have anorexia as I have all the symptoms but I am not seriously underwieght, can anyone help me? Thanks :)