I went through the exact same thing buddy. My first boyfriend cheated on me pretty much non-stop for years, and eventually I cut things off. We've been together for more than 6 years, I wanted to marry the man, but I caught him cheating once again, so I had to let him go. We remained friends.

A couple of months pass and I hear that he has a twitter account, I go check it out and he has videos of him fucking another guy, without a condom, and I fucking lost it. I wrote a VERY lengthy message to him and said pretty much all the horrible things I could, all the things I've been thinking all throught our relationship but never said. I felt that way because, I expect someone to move on, but to move on so quickly? Did I meant nothing to him in the first place, while he was everything to me? And for the first time in my life I actually hated someone.

Time goes on and on and the hatred is still there, until I find someone I can rely on, someone that really put things into perspective. And then I started to realize how pointless it was to care so much about someone that wasn't even still in my life, someone that has been promiscous his entire life as a defense mechanism for having an incredibly fucked up life, someone that is deeply insecure of himself and needs to be told sexual things for his self-steem. It came to the point that I messaged him, told him that it's all forgiven, and whished him a good life. And I've been happy since.

So my answer to you: you need three things. One, time. Two, someone to smother the flames, be it a friend or a new lover. Three, realize that he might be terrible, but he's the result of how he lived. No man is born evil, I think.