It's definitely a tough situation to be in, and sometimes things just don't work. I'd try sitting him down, and telling him you need to have a serious talk. If he doesn't want to, then you know automatically it won't work, but if he will, then try to talk it out, and see if you guys can come up with a solution that works for both of you. Relationships are like a house. When a bulb burns out, you don't find another house, you fix the burnt out bulb and move on. Good luck. I hope things work out for you.
I've been in your shoes. Just make sure it's what you truly want and m try to make sure you both can co-pay entry for your baby. It's really tough but I had to put all differences aside with my ex and we now have a great co-parenting method. We are good friends. I really hope everything goes well for you. I believe in happiness. Find yours. And congrats on baby.