Hi Rosieposie9. I've been there, which is why I could not not respond to your post. The only difference is that my DH's only child (and mine) is the one we have together.
He loves DD but did not want another - beforehand we only spoke about "children", but neither of us specified what we meant. I am an only child and wanted more than one. He is one of three and wanted one... I suspect he would have possibly been amenable to trying for another one if we had had a boy, but I'll never know.
I pleaded and cried for thee years, periodically, explaining my thoughts, my feelings, the yearning, from the time she was 2 until she was 5. It did not work. I could not consider tricking him into it, and I could not persuade him. My choice was therefore a happy three-person family with him or leaving him, a man I love and respect, with whom I've built a good life, for a vague hope of another child. In the end I stopped talking about it and decided that was it, my marriage and family were good as they were and further discussions were fruitless and made both of us sad.
Nobody can tell you what decision might be right for you, or whether you might be able to persuade your DH to reconsider. It helped that my DD never asked for a sibling (something I did as a child, a lot). I am now 43 and the yearning has passed. I wish it could have been different, but the thought doesn't leave me in a flood of tears any longer.