Have you ever been to a psychologist, therapist, counselor (whatever you want to call them)? It really, really does help to have someone to talk to. Unfortunately, an awful lot of kids have been through the kinds of things you have. It's too much to deal with all by yourself, and family may be the last people you want to be around. Have you ever talked to your mother about what she allowed to happen - and didn't she KNOW something was wrong?!?!?! Now to be living with her! I had to say so many things to my mother, and that helped a lot, too.
Even if you get ahold of a "bad" therapist (and there are many, let me tell you!), just putting these things into words helps ease your mind. Do you have health insurance? If not, maybe there's something like a United Way agency in your area that might refer you to somebody who has a sliding scale fee structure.