That rash sounds like no fun. That it moves around sounds like a lymphic sort of thing. I had an allergic reaction to poison oak many years ago that got into the lymph system. Took ~forever~ for the rashes to stop popping up all over.
"Inconclusive" is at least maybe some good news inasmuch as the really bad stuff tends to be better known. I dunno. Not a doctor, and didn't stay at a holiday inn express last night. :-)
I got a rash on my side that itched a couple of years ago that turned out to be shingles. Until I got it myself I had always thought it was just something people got that itched a little bit and then went away. It didn't take me long to find out that there's some very intense pain that comes with it that can linger for a long period of time.
We live and learn.