I am so sorry that you are experiencing these trust-shattering experiences. You've had some superb advice - ACT ON IT, NOW. Don't wait for "something" to happen or for someone to make the call for you. Call Child Protective Services, immediately, and they will contact the police. A full investigation will be conducted and this will include a physical exam. Retrieve any/all physical evidence that may still exist, if you can.
You're a brave person to put your experiences into words and your courage will see you through this horrible part of your life safely and securely onto your healing path. Something that you may want to keep in mind is that your mother is probably being abused, as well. She may be turning a "blind eye" to what's been happening to you because she's probably been threatened that you will be taken away from her, forever, if she does ANYthing that might get this rat-bastid into prison. This is a threat that many abusers use to make sure that there is no interference in their heinous activities.
Take heart, dear one. As I said, you're very brave and this courage will help you to process all that's happened to you. You did nothing to deserve it, and you're NOT a bad person because this monster did what he did to you. You are not responsible for the actions of another adult. This person did all of this to you because he could - that's the only reason. Now, get on the phone, contact CPS, tell them EVERYTHING, and you and your mother will be taken to safety, and the rotten catfish will be thrown into jail.