domestic abuse???

okay so I've been working on things with my ex boyfriend (we dated for a year and three months), we were broken up for about seven months but we never stopped talking or hooking up. I wanted him back but he was busy being sing le and emotionally hurt me a lot. Well in December he came back fully and said he only wanted me, I'm not a bitter person so I forgave him for always putting other girls before me and comparing me to his new girls, because I really love him. And I believe he loves me too he just loves differently.. he's never hit me before when we dated or saw eachother those months we were broken up. But this time around when we've been serious he's been pretty aggressive. When we dated I used to slap him and punched him once in the face and I know it was wrong but i haven't been abusive since. I'm 5ft tall 95 pounds. He's like 6ft and 160 pounds. I'm sorry this is long I just have slot to explain so you all don't think he's a bad person. So one night in December after we agreed to work on things for real this time, he fought with me over politics since we don't agree one bit on that topic. And wouldn't let me in his house and it was winter and kept pushing me outside and said he'd throw my stuff outside (I live with him)  and started calling me a dirty Mexican I was disgusting and this other girl he left me for awhile ago was prettier than me and richer, and his mom slapped him and let me in and he started threatening me saying he was going to get someone to hurt me for having his mom slap him. That night I got drunk and went off Molly and left with a guy and just gave him oral. Nothing else. The next day my "boyfriend" apologized and said we're still together. I didn't tell him anything about it. Some nights after that I'd come home drunk and he'd be mad and slap me so hard and pin me to the bed and slap me a couple times. Not too bad. I could barely remeber. Last night I told him about the guy I messed with.... and he turned into a different person. He hit me so hard in the stomach I couldn't breathe he hit me repeatedly in the face I have bruises on my right temple a bruise in the middle of my nose, a little under my eye. My arm. My leg. He's a strong guy and kept slapping me and punched my arms and legs so hard. I thought he was going to kill me.. but I love him and today he told me "I'll give you a second chance" because we don't want to be over... I just don't know why he's been abusive. He was never like this.. my lip was busted and I just I don't know what to do. I hit him first I scaratxhed him I slapped him kicked him threw all his clothes all over his room poured soda on literally all his clothes and him and his floor and bed and after that that was what triggered him. I was in the wrong I know I provoked him because I know his bad anger problems. But I don't know what to do