I agree with what some of the other posters have said, I think it's hard sometimes to really get into the pregnancy side of things cos it's not actually happening to them.
But I must say when you mentioned he lost a baby (like starssky was saying too) it could have something to do with the loss. He may be really scared that something could happen to this bub. And if the loss ended up with his previous relationship breaking down he could be worried about the same thing happening. Maybe?
Hope all works out for you in the end I'm sure it will, all the best