S.B.
Hi D., I'm only 31 but suffer from the same issues. I've never had any kids and really can't think of any reason why I'd be this way. Physiologically, we are probably quite different but I wanted to pass along the title of a book that you could try (just in case it's an emotional issue--I've been tested out the wazoo for physical reasons why I'm the way I am). You can get it at the library: Passionate Marriage by Dr.David Schnarch. It's been very helpful in my relationship with my almost-husband. :) Here's the website: http://passionatemarriage.com/
Good luck.