Should I be blaming myself this much for my breakup?

I know I shouldn't care what one person thinks, but I do. Because that one person is my ex- and after going through so much together over 4 years, this feeling of hatred that he seems to have towards me is unbearable.
It's been three months since we split- it was a complicated relationship and we both made mistakes. However, in the end, I did a couple of petty things (we're not talking cheating or anything really sinister, just really petty stuff) that ended up killing the relationship for good.
Now, I have always acknowledged and accepted that I f-ed up, and although me and my ex don't talk anymore, on the occasions that I have contacted him, he remains cold and almost cruel to me. He said that he doesn't harbour any bad feeling toward me but he isn't nice or respectful towards me at all.
I'm not really sure how I should feel- I feel like a piece of sh*t because that seems to be how how feels about me. I can't help but feel guilty and blame myself for everything. But- and it's a big but- he made mistakes too. Mistakes that suggest cheating, or at least, intent to cheat. So when I compare that against anything I ever did to him (being moody, kinda petty, a little argumentative at times), it just doesn't seem comparable. He was never really THAT sorry for the things I found out about him and forgave him for, yet he has made it clear that he isn't going to forgive me for things that are so minor in comparison.
I don't know how I should feel- on one hand I know I acted like a jerk just before we split, so I've been beating myself up about it and struggling to forgive myself. But at the same time, how is it that he seemingly gets to walk away without any guilt/responsibility when he did things that were worse? Should I be mad with myself, or him? I really don't know.