You are going to have these feelings but try not to be cold to XH as he will see it as you just plain being a bit## and will serve as a reason to keep doing what he is even longer.
Be distant but be friendly.
Does he get sex every time he is with you if so maybe you should back off on that although it is up too you. right now he has the best of both worlds and you need to show him he can't have it all his way.
If he calls later don't answer. When you do talk in a day or two and he asks where you were tell him out because you were right !!(go out with some friends and have a good time). Be vague about what you are doing it will serve to make him jealous (Hopefully) YA know just because you are pregnant doesn't mean you are not attractive and can't be hit on,
You need to start making a life for you and not worry about what H is thinking or doing right now.
It sounds to me like he Might be in a Mid Life Crisis and it may be awhile before he comes back to earth.
How old are you two anyway?
JAK
You don't get to choose how you're going to die. Or when, you can only decide how you're going to live now. ~Joan Baez