Your mom really needs to go to counseling. Maybe she doesn't realize how horrible she's treating you, and needs to have it pointed out to her, maybe that would help.
If she does realize though, but continues in her actions, you should tell someone. School counselor, teacher, aunt or uncle, someone that can intervene. Letting it go on is so not good for you. IMHO. Don't mean to sound uppity or know-it-all ish. Just sounds like a bad situation, no pity, just concern.