So frustrated!

I'm 3 days away from the beginning of my fertile window and we still don't have a confirmed donor. We opted to do the known donor method and the donor we chose said yes MOOOONTHS ago and every week up until November when I ovulated and it was showtime. He had some health concerns of his and we understood. I don't know how to bring it up now to ask where he stands or if he's backing out. Ladies, if you're using donor sperm, what are you doing? Friend? Known donor? Or buying? If you searched online for your donor, where did you go?