Partner just ups and leaves

My bf just gets up and walks out the door , doesn’t speak just grabs his keys and head out. In the past I’ve told him I don’t like that and he should tell me where he’s going. My reasoning is we have a 22 month old and I am currently 31 weeks pregnant . This morning I hear our son in his crib calling for his daddy. So I waited a few mins I can hear his dad in his game room , I let 3 mins go by and my baby still calling for him . so I get up and get him . He walks out walks right passed us and leaves.... I just want to know is that normal? I felt so bad for my son , he chased his dad all the way to the door just to have it shut in his face and of course he cried... I’m starting to feel like he doesn’t want to be around us, He’s made comments about how when the new baby comes he’s not going to be here as much and how he’s going to get a second just to keep busy. My mom has been coming over more to help me with my son I’m Supposed to be on bed rest but it’s in possible when my bf leaves and doesn’t say anything. I don’t wanna make a big deal out of it but he’s acting different. And it’s starting to make me feel like a single parent and like he’s going to leave and never come back.