Talk to him! Guys aren't mind readers. Be straightforward and clear about how you're feeling, and if he isn't a complete piece of shit, he'll listen to you and adjust properly. If he's committed to you and the child, then he shouldn't have a problem with this. Maybe talk to him and see how he's feeling as well? Having a baby is a big step and can add a lot of stress to both parties, so it's important to make sure both momma and daddy are doing ok :)