It is hard when the grief of a miscarriage (especially when as late as yours) is unequally felt between the parents.
My dh (after I had had a few miscarriages) got to the point where he no longer got excited by me being pregnant, he shut off his emotions from connecting with the unborn child. This meant that even more than previously he no longer felt the grief of the lost pregnancy.
He openly admitted he did not feel the pain of the miscarriages as I did, he did not have the hormonal upset either. It got to a point where he said no more. This was more due to his concern over my wellbeing rather than anything else.
I think that when men see their wives distressed from miscarriage, it is easier for them to say no more, and try to protect thier wives and themselves from the potential repeat of the upset.
Men don't often feel the need to procreate as women often do. The fact that your dh had already conceeded to try with a timeframe limit, suggests that he was going for child number 3 for you, rather than because he wanted it. So now he would see the risk of more upset with the risk of another miscarriage, as a step too far. He wants to prevent more upset and this outweighs anything else.
He can't possibly understand the space that needs to be filled in the family structure.
My dh each time after later miscarriages said no more. But within a few months, when he has seen me less grief-filled, he has relented and agreed to try again. Much reassurance from me that I would not fall to pieces if it happened again helped.
However the difference between us is that my dh has always been more open to the possibility of a further child (not actively seeking it, but not so anti), and the main reason for him saying no to me, was because of his concern for me.
After 12 miscarriages over 4 years and some counselling for myself, I am in a much better place. The grief will always be there, and the gap at the table remains unfilled, but I can truely say that now I am much easier with the prospect of us staying as a family with three children, rather than the four that I always dreamt of having. Due to my age, the likelyhood of me having a successful pregnancy now is extremely low, and the grief of losing my fertility was part of the grief process that I have been through with the counselling.
Your dh may or may not change his mind with time, but I would be surprised if he did while the grief is still so raw in you. Have you considered counselling for the grief of your loss? Or what about counselling where you could have a neutral person helping you both to come to a concensus on whether to try for another baby would be the best for all the family?
Sorry this is so long, but I wanted to try to say that I have been in a similar place to you, and can understand some of your pain.