There are probably many different opinions on what to do here. My personal opinion is that until you resolve things it isn't fair to your bf to hold onto your XH. There is no way of knowing what your XH is thinking or doing. Trying to interpret action or inaction is entirely speculation. The only way you would know is to talk to him. Usually I would suggest that you let your X take the initiative and make contact if he is going to. In your case, I guess I would suggest calling him, make small talk, and catch up on his life. Perhaps during the convo he'd say something that confirmed he was over you, in love with this new woman, and fully intending to marry her. At that point I would suggest letting go and moving on with your own life.
That being said, part of me thinks that it's not fair to him or his fiancee' to check on whether he still has feelings for you. He's the father of her child and I guess if they have a chance to make a family I wouldn't want to be the one to stand between them. I guess as long as you could confirm he's happy and content with his new life it would probably be okay to contact him, just for closure. And if he says "I'm not over you. I still love you." then I don't know what to say.
But this is hard advice to give. Hopefully others have an opinion. In a perfect world everyone involved would live happily ever after.
In the end, it's not the years in your life that count. It's the life in your years. Abraham Lincoln
It is hard to fail, but it is worse never to have tried to succeed. Theodore Roosevelt
