What an ordeal you have been though. I am not at all surprised you have a hole in your heart. Not only did you have the emotional pain of losing the baby, but you ended up with all kinds of physical complications to resolve. And it sounds as if you aren't quite physically healed yet. I can kind of see where your husband is coming from. It's been 8 months since the miscarriage and you're only "almost" physically healed. I don't know how old your boys are, so I'm kind of guessing that the 4 miscarriages have all happened since the boys were born ?? I'm also guessing that your husband is feeling guilty because "he did this to you" by getting you pregnant, and he had to have been really scared that he might lose you somewhere along the road. And he just doesn't want to go through the guilt and horror of that all over again. His desire not to try again is prompted by his love for you, although it sounds as if you feel walled in by that desire.
So, the next set of questions are physical. Do the doc's have any idea what caused the 4 miscarriages ? The only way I can see it would make sense to go foward with a pregnancy would be to mitigate the factors that might have contributed to them. But if they don't know what caused you to miscarry, then you might be getting pregnant just to go through another miscarriage and another D&C -- which would probably be rather very after this last one.
So, then there's the emptiness inside that probably didn't get dealt with so much while you were more actively fighting the complications. It's normal to greave, and it's normal for that process to last a while. I am again guessing, that you are mourning the loss of the baby, and coming to terms with the reality that there isn't a baby moving into your home. Given the fact that the miscarriage was in March, had it not happened, you would have a baby in your arms right now. But they remain empty.
And that is incredibly hard to deal with. It's also hard because everyone else has moved on. And they don't understand, since the miscarriage happened so "long ago", that you are still grieving. Do you have a friend you can talk with ? the more you talk out your feelings, the healthier you will be. If there isn't a friend you can unload on, why don't you try keeping a journal. Write it all down, the hopes and dreams you had for your baby, the joy you had when you discovered you were pregnant, and the devastation of losing the baby. Write it all down. And write it all out again and again, as the emotions crop up, read what you've written and cry it out. You need to be able to look at the horror this brought to you, in order to move on, whether that moving on would mean getting pregnant again, or whether it means that you end up raising only 2 of your own children.
And then we come to the reality that you want more children and your husband does not. You would like to adopt, and he does not. I'm guessing (again) that he isn't trying to be cruel, but that he is simply happy with 2 boys and doesn't need to have more children to make him feel satisfied with family life. while you would like to try again, and feel "shut down" and maybe "shut out" here, it does take two parents to make a baby, and it would be best to go into the process with both of you on the same page.
So, if he doesn't want to risk losing his wife and he doesn't want to adopt, once you've dealt with your aching heart, how can you funnel that love that's inside you ? (well, yes, you do have 2 boys already, but I'm guessing you have more love and are looking to add kids to the mix to give that love an additional outlet)
Have you ever thought about babysitting infants in your home? You could have up to 4 young kids in your home while their moms go to work. I had no choice but to work when all 4 of my kids were little, and it's very hard to find a loving and positive environment for infants. When they get to nursery school age, its a whole lot easier, but there are still those moms who would so love to find a mom who would like to co-parent with her while she works. 3 of the babysitters I hired were wonderful. One was part of a farm family, and she was like an extra grandparent. She really loved my eldest, then #2, when she came along. Those girls are now 27 & 25, and we still exchange Xmas cards! She went way beyond the call of duty, keeping my kids and feeding them supper when I got stuck working late, never asking for more money in return. (In fact, whenever I got raises, I forced her to take raises, too, because without her, I would not have been able to earn those payraises.) The other two women were closer to my age, and they, too, acted as extra moms for me. I was able to share concerns I had about my kids, and get their feedback, because they saw my children all day long. While I have a wonderful husband, there were still times when I felt at a loss to interpret what I was seeing -- and adding one more "mom-brain" to the mix was a godsend.
Having had that kind of experience as a working mom, I can tell you that if you are willing to put your arms around a baby you send home at the end of each day, and are willing to love them, and help the biological mom parent that baby, you will be doing SO much for both the babies and their moms, that you will be remembered all their lives. It isn't the same as having your own baby, but I put it out there as a possible compromise wherein you don't attempt to have another pregnancy because your husband doesn't dare to go through that again, and he doesn't want to adopt, but you still have the opportunity to share the love in your heart with people, including babies, who truly need that love, and who would benefit greatly from having a home environment for daycare, rather than a larger daycare setting that is "more sterile" because it is more of a business than a place where love happens.
I wouldn't necessarily jump into the future at this point, however. Get through the anniversary of the miscarriage before you make any decisions. Grieving takes time, so try to be patient with yourself while you do that grieving. You had a baby die, just as much as someone who carried the baby all 9 months and still lost it. So the hole in your heart makes all kinds of sense. Just keep on keeping on . . . one day at a time. It's hard, and healing takes time so give yourself some leeway, and wade your way through life until you begin to feel healed in your heart.