I NEED ADVICE‼️

So I’m 27 weeks pregnant and although me and baby’s dad have not had the greatest start I thought we’d figured things out. So today he told me he met someone and they’re going to start dating and even though I told him I’m happy for him this bothers me. Just a few weeks ago we talked about moving in together and actually giving things another shot. I’m so shocked but at the same time I expected something because of how distant he became. Idk what I should do or say. The angry part of me wants to cut all communication and not even inform him of our daughters birth. The mature part of me just says let it go. Honestly , I just want to hurt his feelings like he’s hurt mine. Helppppp‼️