Upset about something from a year ago?

So when me and my bf first got together (2 years ago) he was going through some stuff, but at first the relationship was great. Then it ended up getting really bad, he would scream at me and I mean SCREAM, call me horrible names, start fights over literally nothing, punch things that kind of stuff. I spent the majority of my time bending over backwards to avoid a fight and when one would start I would just sit there and take it all and cry. This went on for a very long time but I loved him and just wanted to help, finally after about a year of this, he changed, like genuinely changed and has stayed that way for what is almost the past year. We finally have a healthy relationship, but I find myself struggling now. Now that we have a good relationship I realise just how bad he treated me and how much it affected me. He started struggling with the guilt of what he had done to me when he first started to calm down but I always just told him it wasn’t his fault which I suffered in silence. I’ve brought it up a few times but he just says “it’s in the past” which I agree with, but I never spoke about it to anyone. I don’t want to seem like I’m trying to punish him now for it when he has changed and been doing so well for so long, but the more I think about the beginning the more upset I get. I know that this is all my fault and I should have left when it was bad and I have no right to be upset now, I really don’t know what to do to get over this.

Edit: This might sound bad but i genuinely feel so validated by the people saying that he was being abusive, Ive tried to tell him more recently that he was abusive towards me at the beginning of the relationship and he completely turned it on me because it was “a horrible thing to say to someone you love” and I was “exaggerating” so once again I dropped it. If I get nothing else from this post, I’m so relieved to hear that I wasn’t just exaggerating and that he was genuinely abusing me.