I don't think there is a compromise. One of you has to give in. The thing is, you can't do it with a sword hanging over your head.
DH wanted another child from when DS1 was 8 months old. I was hideously ill throughout my first pg., followed by a week of induced labour..and lots and lots of different issues that led me to say I wouldn't have another child EVER. I was so ashamed of this, but I was very brazen about it. DS1 was then a crap sleeper, I had PND that nearly had me jumping off a bridge, and walking out several times.
I had a little more time on my side, but not much. In the end DS1 was nearly 4 when DS2 was born. DH seriously caught me on the hop and I sort of didn't object to the idea that strongly at that particular moment, and that night he was conceived.
It was another grim 9 months, I was even more ill physically with the second pg., and the only saving grace was an incredibly managed birth, and this one slept. I had terrible PND again, and when DS2 was 2, last year, I left. Only to come back, because I could't leave the boys. Things have changed alot since then... but underlying all of it was my monumental resentment that I knew it was going to be hideous, and I also felt as if my needs were, once again (as always with a mother) way down the list.
The really really great thing to have come out of it is that the boys have always been really "there" for each other. Even among the fighting, they adore each other.
And I adore them. If I was given that Saturday over again, I would not have got pregnant, but I cannot imagien my life without DS2 who I love to pieces.
This isn't saying that having another baby is the answer, but just warning you that it could be as awful as you think it's going to be, and YET might still be OK.
Your relationship is going to be stressed, whatever, and maybe you need for your DP to make some major statement about taking on a phenomenal amount of the early months stuff... think about a few years down teh line.
BTW, I was all geared up to go straight back on the anti-d's as soon as necessary, and it still wasn't soon enough, I should've kept them going during the pg. for longer, or gone back on them at labour.
The only time when it can be a slight issue is the last week or so/delivery..but even then, it's something any obstetrician/psychiatrist will know how to handle.
I am thinking of you and wish you well with this hellish situation. There are ways through, but none of them are easy.