Weight issues.. some one help?

im thirteen, and.. i weight 7.12 stone. i dont know how tall i am, but about 5.5ft. my friends tell me im not fat. and i dont generally think i am, but i eat alot. but ive got a different metabilism. and i dont really put on any weight. but ive recently put on abit i think, im so self-concious about it.. and i even tie belts around my belly tightly so i dont look or feel fat. am i wrong? can someone one tell me if im fat?