Why are people so repulsed by me?

i'm a fifteen year old girl, and i cant get a boyfriend for the life of me. i'm plus size, and not the most attractive person ever but i don't think i'm hideous. i've had boyfriends & girlfriends in the past, but i've been single for like a year now. im a really sweet person and people say im cool, so can someone please explain to me what i'm doing wrong?