Of course it is improper for me to try and diagnose you without knowing you, but I can say this: If I were taking a test in graduate school, and I needed to offer an opinion, the descriptions you’re explaining suggest that eating is depleting a great deal of your energy. Too much so, and I would highly recommend talking to a physician. The intensity and range of thoughts you have about food, your weight, the exercising, and self-esteem issues are more intense than reasonable for someone your age. The physician can tell you if there is a medical or psychological reason for your symptoms. In either case, I wouldn’t wait. After a while such a diet can throw off some of your normal bodily functions. You’ll want to deal with this sooner rather than later.