I need to get past my insecurities?

I cant stay happy anymore because all i can think about is my hatred towards food and my guilt for eating junky foods like carbs and starches and sugars. I'm 17 and 5 foot 6 and weigh about 130 pounds and i know i look healthy and im not technically overweight, but when i stand next to my friends i cant help but feel larger. I kid you not all of my closest friends are no bigger than a size 3. I cant concentrate on things anymore like school work or reading because my mind wanders and i start thinking im hungry when im not and then the whole guilt circle kicks in again. I'm so sick of this feeling and i need it to stop, but i dont know how to let it go. I hate myself to my very core and i have to avoid mirrors because when i see my body i feel such shame and disappointment in myself. I cant control this anymore what do i do