How do I know if I'm being abused?

Okay. So, for the past two years now, my parents have been trying to get a divorce. Since then, in 2009, I started cutting my arms kind of deeply with razors. I was twelve. I cut my hair really short, and I went to school, and people would ask me if I was emo, or if I was goth. I told them that I wasn't and to screw off. Then, since I'm in orchestra, and a really high up chair, my orchestra teachers got concerned, but, I only found that out this year. I had gotten a therapist to talk to about my problems, but I never wanted to. Ever. I like her, but, I don't like having to explain my life to someone I didn't know. Then, I started to cut more. In 2010, my parents started a rotation since my dad wanted to see me and my brothers more. But, that changed when my Guardian Ad Litem stepped in and screwed up our lives, so we're living with dad. Since then, in August 2010, there was a huge fight between my mom, Dad, two cousins, Grandma, my older brother, who's sixteen, and me. Thirteen year old Courtney. Since then, my dad's lost his eyesight in his right eye, and we never have money. He takes our money and is always asking us, a thirteen year old, and a sixteen year old, for money. We say no, then he gets mad and runs a guilt trip, saying that we hit him in his eyes, when I never fought him. I tried to break up the fight. He comes at me like he's going to hit me, and he slaps me in my mouth. I can't help but cry, and it hurts, knowing that it's like this. Today and yesterday, I had to go to school with a swollen lip. He's hit me in the head, and he's slapped me. But, I never told anyone like my Grandmother told me.He once asked me to give him $66 for the mortgage, which I didn't have, and when I gave him my cash, he threw it at me and he told me that he can't trust his own kids, how we made him lose his eye, how my mother and I plot against him, trying to get him out of the house. I always take care of both of my brothers. The oldest is 16, and the youngest is 7. They both have autism, so I have to be the one to take care of both of them, food and hygiene wise. He leaves and works, leaving us with his cousins from 3:45pm-9;00pm at nit on Weekdays from Mon.-Thurs., and they've told him that when I cal my mother from there, I tell her they don't feed us,which I NEVER said. Plus, They've talked behind my back, and I've heard them. "Crybaby, Liar, Snitch," etc. My cousins all live in one house, and they are: 1 55 year old woman, and I'm cool with my cousins L(21) and P(23, had surgery). But T., The 24 year-old, who lives with her son there, talks smack about me, and my other cousin tells me. She thinks I'm a liar, and she tells her 8 year old, Elijah this, who tells me, but I love her son. I hate it there. Except for P. and L. But, anyway, then, this school year ((2010-2011)), I've had a hard time focusing. I've gotten kicked out of AAP and put in general, my father yells at me and always bad mouths my mother, and my grandmother, who's ARM he broke! SHE HAD TO HAVE SURGERY BECAUSE OF HIM! I HATE HIM! I ran away once, down the street to where my Grandma and Grandpa and Mom lives, and they police made me go back to his house. He tells me about his lost right eye, about how he can trust us, and recently, he went to jail for Hit&Run and expired car tags and expired license and I was in the car. I walked all the way to my Grandparents and mom's house ((5 miles.I was in a different neighborhood)) and now I have a tiny tear in my shoulder form that accident and he didn't call me or my brothers at our Grandmother's house for 7 days. I missed my All State Orchestra audition, and everything because of my shoulder, and he didn't ask me how I was feeling at all. He asked me why I told them. He still talks about how I'm so terrible, and how I always take up for Mommy, and how I plot against him, and how I'm so stupid for getting kicked out of AAP, and how they're liars. then, I try to avoid him. I don't even feel like doing anything anymore. I don't want to go to school, I don't want to play my instrument, I always put up a happy facade, but I'm not. I stay in my room all weekend and I'm depressed. I think about killing myself, about killing my father, about how would life be if I died...Am I being abused by my father? am I depressed...? What's wrong with me? Thanks.