Why are they so mean in school?

girls in school thinks im stuck up and ugly…I have a REALLLYYY low self esteem issue its sooo bad that I cant look in poeple eyes strait.so when poeple are talkign to me I dont look at them so they think im rude.they dont even no me and they just see me once in tha hall and juge me.they say things like(ew her hairs fake) her nails are fake.when there are really pretty famous women with fake hair and nails…even when im wereing like really nice clothes they still find something about it to mean to say.antoher thing is I guess because im balck and where hollister and skirts and pink a lot andi dont talk so “hood” im an oreo.I always ask my self then what is a black girl supose to act like.and for some oddd reason they also calls me a slut just because my friend I guess slep with 2 guys at once and by me hanging out with her they think im the same way to.but im not gona drop a 5 year friend ship just to be cool thats not me.I have talked to her about that…anyways I gues im asking well I don’t know really what im asking I I jsuts need good advice THANKS