Am I wrong for the way I feel????

I have been with my man for almost a year in August,  he has a 3 year old daughter and 1 and half year old son. We're expecting my 1st and his 3rd child which is going to be a sweet, handsome boy in September. Okay don't get me wrong I treat his kids like they're my own even though they don't live with us at the moment. We see them every chance we can.  
Now getting to the point, I feel like he hasn't tried to connect with our baby like he does his other two children.  And I'm not sure if it's because I'm sensitive to the fact that anything we talk about that deals with our baby he shows as if he either knows it all because he has two already or doesn't really care about it right then and there or doesn't show much interest. I'll ask him to come talk to baby and feel his little kicks getting stronger and he shows little interest except when he feels like it. He's like sat down and talked to him but not like enage with him like I do reading books now, singing to him in the shower (my most sensitive moment lol)  Idk if its a man thing that they don't connect until after the birth or what ???? But It bothers me a lot, we've tried talking about how I feel and we just get into little petty arguments that leads me to be outrageously angry because I don't want my first born/child to be treated any differently then the rest. Idk if it's like a jealously thing going on seeing how connects he is with his other children but I love them like my own that's why I'm so confused....  I want to feel that connection between daddy and baby in my belly and I don't see it. My fiancé has his moments where he'll talk about how excited he is can't wait til baby is here and how blessed he feels... But idk !!!! Am I wrong on how I feel ??????