Are you alone with him a lot? Has this been going on for a long time? Is there anyone in the family that would protect you? If not you need to find someone outside the family, like a guidance counselor or a pastor who can get some help for you. You shouldn't think you've done something wrong, what's being done to you is wrong and it's unsafe. Are you a minor? I think you may need an adult to help with going to the police, not sure about that.