Do I let it go

This is kinda bad and I need advice. Me and an ex of mine actively tried to get pregnant but everything moved so fast we was foolishly looking for love , we moved in together and got pregnant 2 months into knowing eachother , he was great tbh I just had to move out because I wasn't feeling it so I did , 2 months later we hung out at his place , had sex an was still pregnant but to my surprise he had a new girlfriend I didn't know about. So basically he was playing both of us. I cut him off because he said he still wanted to be around me even having a girlfriend but never included our kid in anything it was always based on sex. Well I told her I was pregnant , and we had been sleeping together and she did not care they are still together today and not once has he met his child who is now 3 months old. It makes me sick to my damn stomach how a man doesn't want to even meet his son and how a woman can lay with a man and love him knowing he has a kid and hasn't even met him . It's weird as fuck