Trying2bemum that does sound very hard for you both, and particularly hard on you with all that comes in the first trimester, both physically and emotionally.
I constantly feel like I don't have the brain space/battery power to engage with the world properly at the moment, and that has included helping DH get into the swing of things with this pregnancy properly, I'm ashamed to say. My app asks how I feel every day and each time I click 'overwhelmed'. We do have more grumpy exchanges than usual at the moment at home. It's probably fairly common.
I worked with a guy years ago who had a full on meltdown about "fatherhood" while his wife was expecting. He'd gone and read lots of philosophy and classical literature on the subject and then decided he wasn't good enough for that. Took his wife ages to dig him out of it. Once the baby was born he couldn't stop saying how, actually, it's just the little things she needs: food, nappies, cuddles. I have to admit, guiltily, it was quite amusing. He's got 3 now!
For me, even after years of TTC, it has also crossed my mind a couple of times lately that our lives won't be the same etc. There's an element of fear there too. I haven't shared it with DH and just assumed that's quite normal. I think my DH thinks it too.
Has your DH got experience of families with young kids? It's not as absolute as 'it's all over', as far as I can tell, it's more shades of grey. Can he spend some time with some nice, normal new parents, who can show him that it's not the end, it's just different. Must be particularly hard for him around all the new year stuff which gets a bit existential anyway. Hopefully he'll agree to get some help. At least he's named all the worries, I suppose.