No, you aren't being reasonable! He needs to see your side and learn to understand that he has to ease into disciplining your kids. He can't just walk back in your lives and start running things the way he thinks is best. You've had a schedule and plan for your child and he's somewhat disrupting it. Talk to him and let him know that it's weird for you.
I'm going through something kind of like this I'm 19w2d with my second my boyfriend is the father to both kids my son is 5 and we have been of and on since middle school and the times that we were seperated he really wasn't in his son's life now we are living together and expecting #2 and its hard for me when he discipline our child because I'm so use to it being just me doing that. We got in a heated argument the other day because I asked him why did he punish our child and he told me its his child too and he should be able to discipline him without me questioning him but I felt like he shouldn't have been punished for what he was doing bit I want to know am I not being reasonable? And as a response to your post as I'm going through the same thing I think it will just take time getting use to I just haven't yet and we have been living together for 9 months now.
Seems hard to do ima ftm and the father still with me just thinking about I want to be the only one holding the baby or my mom no one els!