Help boyfriend probs.

Hello. My names Catelyn & Im dating a guy name Bradley. We've been dating for about a year now, our second month in, I got tired of the boring sex. So I called my ex & we had really good sex. About three weeks later, I figured out that I'm pregnant. I told my boyfriend that I cheated and why I did it. He got super mad and started hurting me. I could tell I hurt him more though. About a week later we were alright & both guys said get an abortion. So I did. Two weeks later it was back to that boring sex. He loves it every single time. I told him that its still boring and he started throwing things and it became angry sex. Anyways that night I went to go see my ex because it was obvious we still loved eachother. We didnt have sex but we had a really fun time. At the end of the night he walked me home and we passed an ally that I heard familiar moans. So we both walked down the alley thinking someone we knew was hurt but no. It was my boyfriend ! He was sticking his penis in another girl. So I went off and he said that he was sorry and blah blah blah. I really don't know who to choose because Bradley said if I dont stay with him he's going to kill himself. Please help !