I am not a doctor or psychologist, but I am a personal trainer and a woman that struggled with an eating disorder for many many years. It sounds to me like willpower isn't the issue here, it sounds to me like an eating disorder or at least the beginning of one. Your story is very familiar to mine. I strongly suggest you see your doctor or perhaps a counsellor at your university. It's a slippersy slope and it's very difficult to remedy these things alone. Please let me know if I can help you in anyway. Sometimes it's helpful just to talk with someone that has been there. Hugs to you!!