abuse in relationship

Right this has been going through my head all week, as I’m not sure what’s right and wrong and I’m partly to blame for the situation on New Year’s eve me and my boyfriend went round his sisters and got drunk. The night ended badly as we both had to much to drink. I don’t remember much just the bad bits. I was told I punched my boyfriend which I do not remember by him... I just remember him dragging me by hair, pushing me to the floor outside, grabbing my arms and then when we returned home he strangled me in the bed. I woke up with bruises all over my arms my knees and a little bruise on my neck. I don’t no if this is acceptable even if I did apparently punch him as I would have had to be wound up to do that and this is not the first time this has happened. But I just wrote it off and never said anything to him I apologized to him but nothing was said back to me. I feel bad and feel as if I have no legs to stand on because I was in the wrong myself