If it were a fungal infection it would itch -- does it? If it were a yeast infection, and I don't see how it could be candida because it's exposed too much to the air for that one, it would smell. Does it? Have you bought any new clothing such as new underwear or perhaps new sheets you might be having an allergic reaction to? Any new source of abrasion? As for doctors, you should never trust doctors completely anymore than you would anyone else, but when you've seen four different doctors and they say the same thing, it's hard to discount them all. The problem with looking at medical journal "sites" is that most studies aren't done very well. They are steps in investigating more involved things very often or are paid for by companies selling something, such as pharmaceutical companies; it's very difficult for even a doctor to tell good ones from bad and only those who do research for a living can really tell. As long as you have a rash and it doesn't go away you should keep looking for an answer, but it just doesn't sound like yeast or the more common external rashes in that area which itch a lot.
"My mind is just wrapped up in the 5-7% statistic of potential resistance. "
Can you explain what the docs said about resistance and why they are convinced it is gone? When did you get the idea there was resistance, and did you discuss it with them?
After you explain, it will be easier to figure how you are thinking.