I agree with everything Leed and Sannah said. It sounds to me like your brain erased bits and pieces of the molestations to protect ifself. And some day, those things might come back. (I'm going through this same thing right now, and it is breaking me). It's horrifying, and I sincerely hope you get out ASAP and report that monster. You've gotta have a friend somewhere out there, or a relative that can take you in. Your mom's enabling the behavior by looking the other way...this has to stop. God forbid you have a daughter and she wants to have her granddaughter spend the night. Because we all know how THAT will end up.
And yes REPORT HIM. Look at that miscreant Jerry Sandusky, if they can bust that monster years after the fact (along with the many priests and other people put in positions of trust and power over children), then why not this jerk? You owe him nothing more than a swift kick to the teeth.
Definitely talk to your therapist and don't ever be afraid to stand up and fight for yourself. You're the only one you owe anything to, not him, not your mom, just you. You know that old saying, "We make our bed, we lie in it?" The same applies to him.
All I know is, if some ashhole came into my room and had his junk close enough to me, thinking I was asleep, he'd need a team of surgeons to repair what I ripped off with my own bare hands.
(Sorry, I just REALLY hate these guys, sweetie).