Why do I always wish that I was prettier?

Ever since I started secondry school, I've always wished I was a different person. I hate my hair (curly), I hate my size ( 5ft 8) I hate what I look like and I just hate myself altogether. Theres loads of brilliant, pretty and perfect girls at my school especially now since i'm in year 10. I even feel different, I love biology (which everyone hates) and I love to read books all the time. I'm horrible looking and like the wrong things. Why do I hate myself? :| :(