Mystery Rash

Help! I'm 33 wks and have had a rash on my hands and feet for almost two weeks that no one can diagnose. The dermatologist's office was convinced it's coxsackie. But blood tests for coxsackie (hand, foot and mouth disease) and parvo (5th disease) came back negative.  Meanwhile the rash has become so painful at night that I can't sleep, even with ice packs on my feet. Nothing else helps either. I've tried Benadryl, Benadryl cream and the prescription cream Clobetasol that the dermatologist gave me. Has anyone heard of something like this before?