Sounds like you need to have a deep, clear conversation about this with him. And if he doesn’t change, then it may be time to move on. I’m sorry
I went through a similar thing with my husband. During my first pregnancy, he doted on me - made me coffee every morning, random foot massages, lots of affection, always helping with anything I needed, etc. During my second, it was like night and day. He actually called me lazy bc I was too tired to do much during the first trimester. Played video games all the time, always scrolling on his phone when we were together, etc. It was really, really hurtful. We were even considering separating at one point. Things got a lot better for us after my 2nd was born. We started making our marriage a priority again. We did do couples counseling for a couple of months. We had some very difficult conversations, but I think we've finally entered a stronger era of our marriage. I think things can improve, but it takes effort from both sides and a strong desire to overcome obstacles as a team. It's a lot of hard conversations, compromise, and sometimes making some sacrifices for the sake of the marriage.
I'm just so tired of what feels like the only adult in this relationship and don't know what to do