Need Advice

I’m expecting a second baby with my ex. He didn’t want another baby we messed around and I got pregnet I knew he was dating some one else I didn’t take him serious because we had been seeing each other for the past 5 years and he been with her for 2 I found out about her last Christmas and she did too he broke it of with me and stayed with her in March during visitation exchange we ended up together. I really love him and I find it hard to let go. He was not happy finding out about this new baby he’s made it clear that this will not get us back together he really like this other girl and had plans refuses to let her know he cheated on her when he promised her not to mess around with me during the exchange. I take my fault and blame my self for this situation am in he wants no part during the pregnancy but assured me he will be their for the baby he’s been very responsible with our first son he’s 5 I have no dout he will be with this new baby. I have try moving on I try setting boundaries but I can’t seem to let him go I give in forgive his crap and just wish he would change