How to change people's first impression of me?

I was best friends with this girl this school year (freshman year of high school) and she's really loud and obnoxious. she really didn't treat me right and i'm kinda of slowly leaving her. well a bet this group of people through her...but they don't even really like her except one guy "loves" her, but she turned him down. well they always figured i was stupid and ditsy because i've never really was myself. but i hung out at this one guys pool with some people and it was really fun, but i still feel like they really don't know the real me, and this one is so mean to me and always calls me stupid. but everyone is really nice! also i have a little girls body, not a lot of curves. but i have big boobs and all the boys would touch them when i wasn't looking, and it upset me because i don't want them to only like me for my boobs and to think i'm a slut. even though they know im a prude! which i am..and proud(: so how do i see the real me and forget what they thought i was?