Such a delicate, emotive situation. I too longed for a third child and I can relate to your post in many ways.
Making a baby is a joint decision and both partners need to be on board. In my case, my husband made it abundantly and explicitly clear that he did not want to try for a third child.
He felt that life was chaotic enough and that a third would add far too much stress to our busy lives and marriage. Some factors make a significant difference such as having grandparents or family near by, siblings who get on, good sleeper(s), a solid partnership and also career(s) that are/is not all-consuming.
Looking back, he was right. It took me a long time to accept it and I still feel broody at times. At the same time, I feel incredibly lucky to have two healthy children whom I absolute adore. My life is complete.
I send you my best wishes. It’s not easy and I feel your anguish.