I have a weight problem?

im 15 years old and extremely overweight. it also doesn't help by the fact i have polycystic ovarian syndrome. i weight 18st5lbs, and have lost a stone so far - yes i know this is enormously big. but i really want to lose weight and would like someone to tell me the best way to lose it, at the moment i follow an eating plan but what types of food should i exactly be eating?any help would be appreciated - thankyou.