I just wanted to say that I know exactly what you're going through. I have the same problem. If I itch it, it spreads to the inside of my thighs. I was seen by a doctor a few years ago thinking maybe I had an STD, a boyfriend of mine 3 years ago cheated on me. The doctor said it's a yeast infection. I found using Vagisil helps but doesn't cure it. The doctor told me that yeast is naturally in your body, and it lives on moist surfaces. I usually put baby powder on a few times a day to prevent chaffing and it helps keep it dry down there, although you have to reapply several times a day. Once you get the rash gone I would start using Vagisil and keep using the baby powder. It *****, I know. If nothing helps I would see your doctor and they can prescribe you something but you'd have to continue it even after the infection is gone to keep it from coming back.
Hope this helps!
The lining on my undergarment dose rub on it and seem to irate it.
Sweating and odd odor sound like a fungus or yeast. You need to keep dry. Skin is also more sensative when damp. You sure it wasn't rubbing against clothes or so.
I should also add that i have symptoms similar to a urinary tract infection and that i more than likely have a sinus infection.