Wishing he didn’t get a vasectomy

Me and my husband have 3 kids. 2 are mine and he has one from a previous relationship. When we got married we only had 2 and I gave him an ultimatum. That I wasn’t going to marry him if he didn’t agree to have another because well he didn’t really want another one and I wanted at least 2 of my own. He agreed we got pregnant and had our 3rd boy. He got a vasectomy 6 months after we had our last. I wish on a monthly basis that his vasectomy will fail because well truly I really want one more. I’m mad that I just agreed to it but feel like I don’t have a right to be mad when I told him only one more… I just feel like I’m longing for something I’m never going to have again and I haven’t came to terms that my last is well really my last.