Tired of This

I am currently living with my dad and my sister. My mom is in a different city because my mom and dad are divorced. I don’t get to see her much because of school. The school I’m currently enrolled in is really strict and I’ve already gotten written up for things that aren’t my fault. That is not the reason I am writing this. The real reason is because my sister, who is 9 months younger than me, constantly switches back and forth between being my “friend” and hating me. She constantly makes fun of me; especially in front of friends (both mine and hers). My dad does nothing about it. He says it is my fault, even though I haven’t done anything wrong. My mom has offered to let me move in with her, but that would mean that I would have to leave all of my friends behind, which I can’t do. To top it all off, my ex boyfriend lied to me saying that he wasn’t interested in dating anyone at the moment (we’re still friends), but I just found out that he’s been dating someone for the past few days and didn’t tell me about it. He actually asked for my permission to date her yesterday, saying he wouldn’t date her if I didn’t want him to, even though he’s been dating her. I’ve started cutting myself again after months of quitting. It’s too much to bear and I’m considering taking it a step further. Someone please help.