Miscarriage now relationship problems

We just lost a baby and we were trying again. But now I found out he is taking to his ex fiancé. Just need some advice do I attempt to make it work or just forget about it. We have been together for 3 years. They have been together for 8... He tells me he has no feeling for her. But he tells her that he misses her and is still in love with her... I can't bring a child into this world with him if he wants to be with his ex?