this certainly sounds suspicious for herpes. at this point a type specific herpes igg blood test is the best next course of action.
I have had the same problem. For a few years now . I have had the fluid tested , herpes test blood, and a biopsy done . My primary doctor says its shingles, however I went to see an allergist and he disagrees he prescribed an oral medicine called prednisone and it helps immediately . However , I noticed I still breakout when stressed . There are usually only 2 at the most that appear in the same spot in my mid back and I usually have sharp pains in my upper stomach along with a mild sore throat .