Ok... I don't know if this is the right place to post this or whatever, but I need help dealing with some crap and I didn't know what else to do besides turn to the internet.

I am 16 years old, and I cannot remember the last time I had a break from the almost constant barrage of insults from my mother. I have a B average in school, which most kids my age would kill for, but it isn't good enough or her. I occasionally will get a bad grade on an assignment, and she instantaneously becomes infuriated, telling me that I am on the path to community college, that I am not good enough at everything I do, and that I am going to end up flipping burgers until I die. She insults my weight constantly calling me a fatty or crap like that. I weigh in at 190 but I am 6'2" so I would call that pretty fit. Her perception of time is skewed and she has no rationality in a discussion, she feels that she knows everything, even though she is a college dropout. She doesn't understand that raising a grade can take time, or that I am under immense stress from her, my friends, and school. (I take four AP classes and one honors math course.) There is just no pleasing her. If I try and sit down to have a discussion with her or get into an argument she just unleashes an army of insults and absolutely stupid points. Once I got a C on a math test, and she told me that I didn't care about my future, and claimed that I was purposefully getting bad grades in school just to make her angry! She asked me whether or not I cared about anything! She constantly tells me that I act "entitled", as if I feel that life should be laid out on a golden platter. She spits words at me that I would NEVER say to anyone. These are things that I would NEVER EVEN CONSIDER saying to her. Things she says right in front of my friends, in front of my brother, in front of my father, and nobody tries to help me. I swear it has something to do with her drinking. She doesn't drink heavy alcohol or vodka or something stupid like that, she drinks about four beers a day and maybe one or to glasses of wine. I don't know if this is a cause or symptom. Its as if she has a broken switch, it is either happy, or furious. That is it. I constantly think about the day that I turn 18 and I am out the door, to go live somewhere she cannot get at me. That's two years away. What do I do?