I think what you're doing is unhealthy, and in a way can easily backfire. The type of crash-dieting that you're doing is not going to be able to last forever and then you will quickly gain back the weight you've lost. You're not really allowing your body to develop healthy habits that will last a lifetime. I'd rather take longer to lost weight (if I needed to lose weight) and keep it off and feel healthy than lose weight super fast just to gain it all back.

There's all kind of other issues about self-esteem and self-harm that could be going on here, but I have had a few body issues myself and the thing that made the most difference to me was my father, who is medically trained, explaining to me how I was hurting myself and actually going against want I wanted to accomplish by crash-dieting/starving myself/overexercising.