abusive boyfriend

My boyfriend of 5 years just started getting really abusive over this past year... EVERYTIME we get ito an argument he will throw whatever he hands in his hands at the time at me, or come at me and throw me on the floor or pick up his hands like he wants to hit me. There's been times he has left several marks on me and there's been times I had to defend myself and hit back but it always just leads to him over powering me and throwing me down or scaring me so bad I have to step away... his excuse is "if you talk to me bad or call me names that's what happens" 

Today I was using the restroom and asked him to watch our daughter in the room. We had just gotten back from eating out and our 10 month old was in her car seat and I had to run to the RR. Well I thought he would have common sense and take her out of there cause I was in there for about 10-15minutes when I got out she was still in her car seat and he was passed out snoring asleep on the bed.. I instantly got mad because he already as it is can never do anything right and I think that is so selfish leaving her in there and him falling asleep like that! I admit I blew up and we strayed to argue, and I was going more mad bc he was saying things like "well she ain't complaining" and "I wasn't asleep" when he was snoring!!! and I called him names I prob shouldn't have, he was walking out the room and he came back and starting swatting my legs with a sealed plastic bag while I was holding our daughter. And then I was telling him to stop and got more mad and called him a name again and then he came back and hit me with it again and it hurt!! My legs are red! And then he proceeded to tell me "EVERYTIME you say shit like that to me or call me a name, I'm gonna hit you until you learn you don't talk to me like that" what am I a child? Even then... I feel so stuck and I'm so heartbroken. I thought he was this sweet sincere man that would never dream of hitting me, ever and now that's all he does when he gets mad. I am so broken and all I think about is my daughter and break down!!! She loves him so much but I don't want to let her grow up seeing this... it will destroy her 😭😢😔 I never in my life thought I would be one of those girls you see on tv in an abusive relationship. Why.......