please help? (don't know what forum to post this on)

Okay, I'm really concerned and uncomfortable about it so I made this separate account so it can be like, anonymous(ish)? I'm 15 years old and I've had to go to my dad's house for almost a year now 2/3 times a month. Every time I go over, him and his friend do things to me that I don't want at all and I don't know what to do. They said they'll kill me and my mom if I tell anyone, and she's all I have at this point. He also talks about how he'll send videos (he's taken probably 20+ of me) to so many people I know. I don't want my friends and family to see me like that and I really cant tell anyone but it hurts so bad and I don't know how to keep going. I have to go, he says that my mom can get arrested if I refuse to come to his house, but I'm scheduled to go on Friday and I'm so terrified of it. They've gotten worse and they've never used protection so I'm always afraid that something bad is going to happen, and I always have to come home and tell my mom that I feel sick. She knows that he makes me anxious and she just thinks that I'm still nervous when I come home, but it hurts so bad to even walk after I come home and I don't think I can keep doing this. I can not tell anyone and I don't understand how to keep going like this until I'm 18. I can't do 3 more years. I'm so desperate for help but it's my dad and good daughters don't send their dads to jail. If you have any advice, please tell me. I'm so desperate. 
Edit: I really really cant tell anyone. I can't let him and his friends send those videos anywhere or post them on anything. It's really really bad stuff and I can't let anyone see it, so I don't know what else to do since I can't call the police or tell anyone