It's good to get a man's perspective. I think it's interesting that a man dare not say too much for fear of being told "well you try giving birth"
I think men have been happy to delegate these "life changing events" to women and women for the most part monopolise and take charge. It's perhaps women's work precisely because our only social power resides in this emotional, reproductive labour, and in raising children. Or at least it has been in the past.
Even in our supposedly more equal society women tend to transfix, talk about, plan, support each other, and get excited about these life changing events, most of all involve men, in the centre but most men probably feel peripheral to the process. Brides turn into bridezilla, mum's to be become totally focused on one thing sometimes to the exclusion of their partners.
I think it's underestimated how men might feel this exclusion is a prelude to more of the same......the eventual end point separate beds, lack of sex, getting the blame for everything.
In a more equal society men should be more excited, invested, interested and committed, but they aren't, mostly.
I do though have some empathy with this. I wanted to run away when I was pregnant. It was me actually who feared the life changing consequences. I'm getting married in a few weeks, it's DP who is excited and doing the planning. He is holding my hand reassuring me, because I don't like these big life changing things......there is after all no going back once it's done. I'm probably not alone, there must be other women like me, but who would know.....the pressure to get exited and to plan is hard to avoid.
Maybe try talking to your DH. I think many men especially feel they can't or shouldn't show any anxiety, or that they can't be a damp squib to your bright bonfire. It's ok to feel scared or anxious by the enormity of these changes and commitment. It's how the pair of you deal with it that will set the tone of your relationship. Ultimately though he has a responsibility, and he needs to get his head around it fast.