I had difficulty conceiving with my first child, so I can appreciate a small part of what people who are really desperate feel. As a consequence, after I had my first, I got pregnant really quickly as I didn't want to wait and now happily have 2 boys of 8 and 7 - my 2nd was born when I was 35, so I would not have been eligible to donate. However, I am not sure, even understanding the pain that people go through, whether I could give up something that was part of me, knowing that I would never see any child of mine created. I know that must sound really selfish, but I am sure that that would hold a lot of people back - I think that if it was for my sister or a close relative where I could still have a relationship with the child, I could maybe have coped better.
I sincerely hope that someone less selfish than me comes along to make your dreams come true - best of luck x