This is such a familiar story for me. Our eldest 2 children were both IVF babies (not twins and privately paid for) so having a 3rd was never going to be easy and since we simply could not afford to pay for IVF with 2 young kids at home already (DS would have been 3 and DD 18mths) it actually seemed to be very unlikely.
But even with it seeming like the odds were we wouldn't have a 3rd child DH was really didn't want to have any more. After a lot of talking, he decided that not having a 3rd child was making me much more unhappy than having another child would make him, so we went back to the assisted conception unit and this time managed to get pregnant on clomid so the cost implication wasn't there.
the 3rd pregnancy was sheer hell, I started having incredibly pain in my pelvis when I was 8 weeks pregnant by the time I was 12 weeks pregnant I couldn't walk without crutches, I couldn't sleep for the pain, and as a result of all this I became really depressed, add to the mix gestational diabetes which required insulin injections and lots of hypoglycaemia episodes - it wasn't a pretty picture.
Thankfully DS2 was born healthy and both DH and I feel immediately in love with him and both delighted that we had a 3rd.
Then DS2 became a toddler, and I became unbelievably broody again, I brought up having a 4th with DH but this time he wouldn't be budged, he was happy to go along with the if it happens naturally it happens, but having been with him for 14 years and not using contraception for 13 years the chances were lets say slim! For him he simply couldn't watch me go through another pregnancy, nor did he feel that he could financially support another child
Now here comes the terrible part, and I do regret doing this, and I have owned up to my husband, I bought clomid from an online pharmacy and took it. I did use ovulation kits, and only ovulated once on the clomid, and actually avoided having sex with DH as I couldn't go through with it - But yes I was wrong, I should have done it
So we were in total stale mate, I wanted he didn't, and I was stood ironing one day, and the answer just popped into my head.
Being totally honest with myself, I realised that I missed having a baby in the house, I love my kids, and enjoy being a mum to them, but I adore the baby days, I always have, I am a trained paediatric nurse and working in special care and the baby ward were the absolute highs. The answer to me was fostering.
Fostering fulfilled all my wants, I got to mother a young child again and DH is more than happy, for him having a 4th child meant that he felt even more pressure to financially support another person.
Obviously this might not be the answer for you, I guess I am saying to think about what your motivation is for having another child, and to look at it from all sides and see if there is an answer that makes both you and your husband happy
Hoping that you come up with a solution that makes you both happy, it is great that you can see that this isn't worth splitting up a happy home for :)