I'm sorry to hear this. It's odd that the police aren't doing anything about it.
Going by what you've written, I would suggest calling the local district attorney's office and see what they can do for you.
Also, consider contacting a lawyer. People have sued police departments before. If you don't have money for a lawyer, you do have options --- 1) Some lawyers will take a case on a contingency basis. In other words, they won't charge you up front but when you get a cash settlement, the lawyer takes 1/3 of it. 2) You could get in touch with your local legal aid.
You could also look into suing those who attacked you. Again, a lawyer can help you with all that.