YANBU! AT ALL!
I only have one, I wanted more but similar to yourself my body doesn't tolerate pregnancy well. I had GD, serious spd (also on crutches fucking painful!), then near the end preeclampsia and we both almost died during the birth partly due to me having a heart condition that doesn't show prepregnancy, flares at childbirth and can be fatal for mum up to a month post Partum too. So I was "strongly advised" not to get pregnant again. And I wouldn't have risked leaving dd motherless aside from anything else.
Dd has not suffered as a result of being (to all intents & purposes she has 5 half siblings that she never gets to see) an only child. Indeed given what's happened since (divorce from dad who never maintained proper contact nor paid cm reliably) it's probably a good thing I didn't have more as it was a struggle anyway. She's turned out pretty well though I say so myself - and I've been told by others too recently (planning a surprise for her 18th and that's prompted some feedback).
All those people pressuring you (and I'd be complaining about the hv none of her damn business and bloody unprofessional) are NOT the ones who will be going through a likely extremely difficult pregnancy, childbirth, night wakings, bf etc.
As for "d"h where is his care for YOU?! Does he pull his weight? I'd be tempted to tell him "we can have another when YOU can do the pregnancy, childbirth, bf, ALL the night wakings, give up work for at least a year and do all the weaning, potty training etc" bet he'll shut the fuck up then! And if he doesn't bury him under the patio! I'll alibi you!
Actually on a serious note ask dh this:
So if I DIE as a result of risking another pregnancy exactly how do you think you will cope as a widower of 2 very young children?!
Dd is almost 18, I'm late 40's and its only very recently I've stopped getting this shit from people who I'm friendly with but who don't really know me. I've ended up saying bluntly "I couldn't have any more even though I wanted to" and letting them think whatever reason that might be if they push it I'll say "because it would have killed me!" Then they DO shut up!
I've also friends who don't have children at all, some couldn't (even with various fertility treatments etc, but also a couple have health conditions which prohibit pregnancy), some didn't want (and a few of them got so fed up with people who refused to "get" that, that they started telling people they couldn't - which shouldn't be necessary but I understand why).
Peoples family planning decisions are very personal and nobody else's business, same goes for whether a child was planned - wtf! None of your business what I do in my sex life!
If someone says they're pregnant you congratulate, maybe wish them a healthy pregnancy that's it! When a baby's born you congratulate you don't bug the parents about whether they're having another it's plain rude!
I also have friends who are only children. Only one is unhappy about it and that's because she thinks her parents acted selfishly having her at all! They were much older parents (mid 40's when they had her), already had known health issues that they knew would deteriorate (also genetic) and before she was even out of her teens she was starting to have to take on caring duties. It's put her off having children herself too, she's inherited one of the conditions which is another factor.
The others are perfectly happy as only's and say you don't miss what you never had. They have good friends & good long term relationships, not all have children but not due to being only's.
I've got 2 siblings, I'm Nc with sister and while bro & I get on ok we're not especially close.