Why does he do this?

I accept that I should’ve left him a LONG time ago but I thought I was so in love with him..

Every time he leaves and goes to another girl he tells them about our personal problems, he tells them that it was all me, that I was the problem of the relationship and that’s why he left..

I wasn’t the one that had sex with another girl and a week later with me, I wasn’t the one that got in contact with my ex and went on dates with our child, I wasn’t the one that has tried to leave him over some guy...

I keep blaming myself for this break up, but I know it wasn’t me, the only bad” thing I basically did was go out to clubs a lot. But that’s it I never did the shit he did to me and I’m taking this break up really hard