Our situation was different in that he wanted to adopt and I wanted to do DE. After pulling my hair out trying to explain things to him, I literally put together a binder with everything laid out very linearly, including price tag, percentages, time frame, plan B, etc. When he saw that for our family DE was the only decision that made sense, he thanked me for laying things out so clearly and we were cycling soon after that. Your DE probably thinks that since you already have a genetic child it can happen again, but it's been enough years now and you're getting close to the age when it would be very unlikely (although not impossible) for it to happen. If it is very important for both of you to provide a sib for your child, I would lay that out for him in terms of your emotional and financial resources as well as difference in age of kids. Sometimes guys just don't get the practical aspects of this.