During high school I dated this guy for three years, and since it was so long we did have a relationship that involved sex. Now during this time when I would worry about certain actions that set off alarm bells, I did confide in one person. He always told me that it was an unhealthy relationship, but always finished the discussion saying I should be with him, so I brushed it off as some form of jealousy. After doing some research of my own, I found that several aspects of our relationship fell into the abuse category, but I'm still dealing with accepting that, but that's a whole other discussion.
I'm in college now, but this ex stayed in touch on a regular basis, because we were friends before we dated and it didn't end badly. He's always sort of been around and trying to monopolize my time, but it's been getting worse lately. What happened today is what prompting me to try to finally do something about it.
I went over his house to watch a movie, and I've done this a hundred time before, because on Saturdays his family is always around, and they're really sweet people. After we get there, and he locks the door behind us, he informs me that his family will be gone all day at his younger brothers sporting tournament. Long story short, we end up in his bedroom because he believes that since we had sex in high school he still owns me. He's bigger and stronger than me, so when he pins me down, as much as I struggle, it doesn't work. He's one of those people into domination, so the more I struggle and suffer, the more he enjoys it. So today when he pinned me down, I'm not going to talk about details, but in the end what he was doing hurt so much I agreed to having sex with him later this week just to make it stop. When I got home and looked in the mirror, I saw two big bruises forming on my upper arms when he held me down with his arms, and bruises forming around my wrists where he grabbed me with his hands.
I need to know how to tell him 'No' where he'll actually hear me and listen. I don't want to involve any authorities for several reasons, and I don't have a way to just stay away from him. What do I do?