Sorry I didn't see this at first BD. DH and I did discuss donor. He really wanted to exhaust all possibilities to having his own bio child first, and although he initially shut down DS, he was getting more open to it as our journey went on.
My advice is that you have to follow your heart on this. While I respected his need to make sure he could not have a bio child, I was also incredibly frustrated that my fertility was going downhill as I got older while we spent so much time exploring his issues. My bio clock was on alarm mode day and night. DH is not one for counseling but I picked my moment while we were in NY and was able to convince him to go in with me and talk to someone on staff about the issues. It helped a lot.
Your DP may not feel as you do about having children but he needs to respect your feelings too, and support you.
Now that I say all that I hope it is totally unnecessary advice!!