I think you need to eat. I did more or less the same thing when I was 14, and it's seriously bad for you. As well as being generally unhealthy, it can stunt your growth, permanently. You'll probably get weak and dizzy often, and it can make you really sensitive, emotionally. Starving yourself lowers your metabolism, so you'll lose less weight than if you just exercise, for example. Teenagers really shouldn't try to lose weight at all unless they are morbidly obese, but you said yourself that your weight is normal. You could lose a lot of muscle, which you're never going to get back. If you do this, I guarantee that you'll regret it for the rest of your life.