Im being bullied.....?

im 15, and you would think by this age bullying would stop. but it hasnt, all the girls in my year hate me for absoloutly no reason. im different to them (im not a little slag!), i dont sleep around, i dont have 100 boyfriends a year, infact i've never had a proper boyfriend. they call me names in lessons, in the corridors and they try to turn my friends against me, which they now pretty much have. i've been to the doctors, he said that im stressed out and depressed about it. i havnt been sleeping properly, i bunk school, i dont go to lessons. And cos im in year11 i kinda need to go to all my lessons cos i have exams and stuff soon. but how can i go in when people are picking on me? :/ The school knows all about it and are trying to sort the situation but to be honest i just need some advice on how to deal with everyone hating me and not letting it take over my life :(