My ex got his new hoe pregnant while I was pregnant and now all of a sudden he wants to do the right…

My ex got his new hoe pregnant while I was pregnant and now all of a sudden he wants to do the right thing with her, he moved in with her 40 mins away and he’s gonna try to marry her. I did everything for him and gave him everything and he left me a single mom and he doesn’t help me or show up to see my son and I just have so much hatred towards them i don’t know how to deal with this I feel so shitty that he didn’t try with me but she’s good enough to settle down with and i wasn’t