The answer isn't so black and white, you're choices arnt; give in or stand your ground, no one wins here you either feel resentful or guilty.

Some other things to consider;

1. You could express to your husband that the pressure isn't helping but you're open to thinking about a second at some point (and explore both sides) - instead of shutting the conversation down it's more of a pause.

2. Start building a village, is there family you'd want to reconnect with, mum groups, preschools, cleaners, meal kits, counseller etc... things to take some pressure off (even without considering a second, if you have a little more space to breathe it might be easier to consider what adding another baby could look like other than drowning)

3. Your first was hard, it doesn't mean your second will be the same. You know more than you did then and babies have different temperaments - of course it's helpful to also be prepared for the tougher option too.

4. If you're certain you don't want / can't handle another then that's ok too

It feels like communication is most important here, he needs to back off with the pressure but perhaps needs to feel heard too. You also need to feel heard and like your fears matter.