You have to think of it from his point of view too. I mean, pregnancy doesn't really effect the guys at all. We go threw everything. And asking him to talk to your tummy might just seem retarded to him lol
When the baby is big enough for him to feel kicking, then he might start to come around a little more. It'll start to feel real for him. He'll actually be a part of the pregnancy.
If your in the beginning of your pregnancy, you are going threw all these changes but nothings really changing for him. He goes day to day like nothing has happened.
Either way, sit him down and talk to him. But I am sure he will come around on his own.