I think Andy is on the right track about the yeast infection. I got rashes several times that didn't respond to the usual diaper rash ointments and finally got up the nerve to see a dermatologist. When he examined the rash area, he said that I did have a yeast infection and gave me a prescription for a cream that cleared it up in a few days. A trip to a dermatologist might be a good idea. You will probably only need to go once, you can usually get refills over the phone once he knows about your problem.