Please Help!

My so and I found out we’re pregnant last week. We are telling family this weekend and we told his mom this morning. When his mom got here and we told her, it’s like his entire demeanor changed. She asked him if he was excited and he was like “yeah I guess.” No smile, no anything. I don’t know if I’m over reacting but that really hurt my feelings. His all the sudden lack of emotion just frankly made me feel like shit. He guesses he’s excited for the baby we worked for, for months. How can his family be excited if he acts like he isn’t in the least bit? Am I overreacting? Is this normal? I haven’t said anything or talked with him about it yet, I wanted some advice first.