raped

Hi so I'm doing this anonymously because I've never fully opened up about what happened to me to others, & it's not just me involved in this as well. 3 years ago, I fell madly in love with this guy, & thought he hung the stars in the night sky. Sadly, I was mistaken. After about a year of us dating, I found out he had cheated repeatedly & he became mentally abusive , cutting me off from my friends, cutting me down, etc. months went by with this, but I stayed because I loved him so much. Right around the time I had enough, we found out we were expecting our son. So once again, I stayed. I wanted my son to have the best life possible, to have a family. It quickly turned dark after my son was born, post-birth I wasn't really in a sexual mood, & by all means wasn't up to having sex or anything of that nature (I think this is normal but I'm still not sure). My sons father on the other hand, didn't think that it mattered whether I was or wasn't, The night our son turned a month old, was the first time he raped me. Later I recal him begging me , saying he didn't know why he did it and that he was sorry. I forgave him. And in turn, it happened again, I blamed myself for allowing it to happen. So I stayed. The third time he held me down and raped me while our son was sleeping in his bed next to us... I will never forget his words to me.. why are you crying? Stop it. I'm almost done... As I begged/cried & told him no & that he was raping me .. he still continued. Later, he broke the bathroom door down thinking I was going to hurt myself because of it. I finally got the courage to leave him, because I knew the relationship was unhealthy & I didn't want my son growing up seeing things like that. Fast forward; now, my sons three. He sees his dad, seldom, but he's still apart of his life. I know what it's like to grow up without a father & I didn't want that for my child. But still I'm haunted by the things he's done to me, his excuse is still I don't know why. & it eats my up inside some nights are harder than others, other nights it's a faint memory. It's gotten easier, but when it's hard to handle it's hard.. How do I handle this pain , anger I feel towards my sons father without it affecting my son? 
*NOTE: his father would never do anything to hurt him, I believe that 100% , they have a great bond whenever they're together (seldom as it is) , he loves his dad & I would never do anything to jeopardize that for him. I just needed to vent, or some advice. TIA.