Better self esteem on body image? *teen girl*?

I'm 17, size 4, and I have really low self esteem..not really on that I can achieve anything because I know I have but I hate my body. I never feel comfortable with it and I always feel like I'm fat..I just hate it..I do workout at least 6 days a week and i eat pretty healthy but are there any ways to improve my self esteem/confidence with my self image? Its all I can think about nowadays and I hate that I'm not as skinny as all the girls in my school (it seems) ...if you can help, that would be great :) no negative comments please.