i had a similar experience in high school. I felt self conscious about my weight and shape. The first thing you have to do is remember you are your best friend and that nobody can know exactly what you need better than you do. Make a goal and stick to it. Make it a goal you can reach. Like getting more exercise or eating healthy for a week. Then reward your self with a treat when reach it. I always use the weekends to eat whatever I want. Then get back excercise and eating right on Monday. But you can do whatever you want. And each day is different don't quit just because you may mess up now and then. At your age you should talk to a health professional about what you need because your body is changing and you need certain things in your diet. Hope that helps.