Rash on privates? not an STD i'm positive?

You seem to be POSITIVE to the fact that it is NOT an STD...I hope for your sake it is not..On that note, could be your undergarments, hope they are of cotton material.......Change of bathing soap OR change of laundry detergent...Try to think of the towels that you have used and what they were washed in...Of course NEVER share towels, with ANYONE.....Hope this helps!