My low self esteem is affecting my relationship what can I do about it :/?

I've been suffering from extremely low self esteem since about ninth grade. It's become such a burden on my life. I cover my arms and legs, no skin could show. I hate when people take pictures of me and I always feel like someone is talking about me. My boyfriend thinks im "beautiful" but no matter how sincere he is I can't believe it. Sometimes we get in fights because I want him to tell me the truth, but he tells me that's what he believes (about being pretty). When it comes to clothing, I wear the same outfit (which usually doesn't show body shape) about 3-4 times a week, just because i feel semi okay in it. I cry because I hate myself so much. I'm not sure if this could have triggered this at all but i was physically and mentally abused until I was 12 years old- now im 16. I won't go to prom with my boyfriend because I won't wear a dress. In the summer I literally sweat to death because I wont wear shorts or capris.I never wear jeans only sweats because i don't like any shape being seen. This is affecting my life severly, breaking down crying almost everyday about hating yourself isn't normal im sure. So a little help would be appreciated. Thanks :/