How to coparent?

How do you coparent with a man that still wants to be with you and still tries to be with you? I moved on for good after being cheated on by my child’s father multiple times. I am currently 5 months pregnant now. With both of our first child. I am willing to let him still be around but he likes to try and be around and talk to me about the relationship and getitng back together when he’s still around. Regardless of me letting him know it’ll never be an us again. Anybody have anymore tips? Should I just let him express himself and listen? Or should I ignore him and just act like I didn’t hear it and redirect attention back towards the child........ I need tips! Preferably from someone who has been through strictly coparenting with someone