I second this...though I've never had it I have read about it several times and confirmed that the articles weren't a big joke with my mom the former nurse.
A major culprit of this is leaving on your workout clothes for extended periods of time post workout....especially if you are a heavy sweater....its sort of the same way hanging around in a wet bathing suit can cause this. I make it a point to change at the gym right when I'm done working out just because I've read about this happening before...think about it...when you sweat while working out your undergarments are left damp in exactly the places where you are describing the irritation...bacteria (yeast) thrives in warm, dark, damp places...it makes sense.
Also you said you were showering 3-4 times a day, I don't know but if I were showering that much I know my skin would get super dried out! Over washing can dry out the natural oils and what not in your skin which I assume could ultimately make it worse. I have also heard of the foot fungus spray for under the breasts but I would definitely check with a doctor before using anything like that below the belt if you know what I mean
