I would agree with the others there is a direct relationship between cycling and yeast infections. I suffered from these nasty infections for almost 2 years before we (new gyno and myself) finally found a cure. Here is what my gyno recommended:

1. don't wear your biking shorts any longer than you have too. I now carry a pair of street shorts to change in as soon as I get off the bike.

2. don't wash your gential area with anything other than a baby soap.

3. douche with buttermilk - you need to reculture your vaginal tract. I had up to this point been eating yogurt everyday along with taking oral acidiphilus. My gyno told me this was great for my digestive tract but the healthy bacteria stayed there it never makes it way to your vagina thus the buttermilk douche for it allows for a "direct route" to the problem area.

4. I had to use a three day treatment of difulcan (sp?) as well as a topical vaginal cream - terconazole. My gyno recommended I apply the prescription cream to the external region before every ride and on long rides to reapply at some point during the ride.

I certainly understand what you are going through and I hope you find a treatment that works. It took me several doctors and many different treatment options to finally find the one that works for me. Knock on wood I've been free of yeast infections for 5 months now. I know that does not seem like much been after fighting them continuously for 2 years it seems like heaven.