My mother...

hello all. please excuse my spelling errors as i am typing this as fast as i can. My mother has been a pretty big part of my life ever since i was a child. She takes care of me, takes me to nice places and satisfys me perfectly in all my physical needs. However mentally things begin to change. Ever since i got into highscool i have begun to recieve poor marks. B's and C's and this has caused her a great toll. She calls me "shithead" "###$" "asshole" on the daily. She has beaten me with wooden spoons and belts. She calls me the virus of the household because she doesnt want me to influence my younger brother and sister. She brings a great toll to me mentally, but I still love her because she is my mom. Just recently I taught my brother how to play counter strike because he always sees me playing the game. I go ahead and showed him how to play as he is 12 going on to 13. He is a very high achieving student and my mom crowns him and my older sister(in college) as the jewels of the family. My mom has figured out that my little brother has been playing this game and my mom SCREAMS FOR ME. She shouts her head off to the point where she is throwing things at me and crying saying "how did i get such an asshole in my life". I know i did not do anything wrong but it still hurts a lot personally. she always gives me dirty looks telling me why cant i be like my older sister, and asks me why im a ###$. She cries a lot saying she has been given a terrible burden (me) and wishes i would go away. I have been very close to suicide ( i have aplan ready at any moment) i keep my cell next to me at all times incase i need to dial the police, and i have packed a few thigns incase i want to runaway. Back to one of the MANY scenarios, she goes to little brother telling him never to tlak to me as i am a "virus" that is going to spread my disease to him. (im not trying to be funny at all, she really said this in a serious tone) She tells him I am ###$ of nature and that he is still a good kid and that no one should ever be associated with me. Mind you i live in the smae house as i am a junior in high school. I dont know what to do, I dont want to be placed ina foster home, I know suicide wont solve anything, and running away will only get me back to where i started. please help