I emailed the clinic last Thursday, after reading all the comments from Tertia's blog. I very apologetically told them basically the same thing I told you. I said I had agreed so quickly because I really cared about the recipients and their desire to have a family, but after a week of considering it and being full of anxiety, I knew that I was mentally and physically incapable of enduring another cycle. I said I really struggled to decide this, that I knew it would cause a lot of heartache, but I felt that I should back out.
They didn't contact me for 4 days. Then today, they called. They talked to the recipient family this morning. The recipients said that it was perfectly ok to back out, that it was a long shot anyway, that I was a wonderful human being, that every day they thought of the wonderful gift I'd given them, and that having an only child was perfectly ok.
I cried with relief. I would have been relieved to not do this cycle no matter what, but knowing that I hadn't completely crushed a family I've never met but still care about makes me feel much better. As of today, my profile has been officially retired at the clinic, so I won't be getting myself into a situation like this again.
So I'm retired. That's great. This is a dramatic close to an important part of my life.