boyfriend jokes about having a bay too much

I'm 17 and my boyfriend is 20 he "jokes" about us having a baby way too much. It feels like he isn't joking but is joking. He says random serious thing but puts like a joke on it, lol if that makes sense. He basically talks about it seriously but adds a laugh at the end trying to hide the seriousness. Why? Does he actually want a baby? Is he actually joking? I don't know. What do I do?