What Causes An Itchy Rash On The Back?

six months ago, I had a terrible sore throat. Went to urgent care, put on Zpack. Went to beach and got sunburn. The burn bubbled when I exercised, and I popped the bubbles :( Few days later, I had a terrible itching sensation on my upper abdomen and scratched only to awake with a red, itchy rash.. was bumpy all over (not blistered). When I would exercise, it would get worse and more irritated so I stopped and let it dry out. It lasted a few weeks before it dried up and flaked off, leaving white spots all over my stomach. (possibly b/c i was tan?) there are still a few scars. Last week, I got a small (50 cent piece sized) rash on my rib cage that looked similar. This one bubbled. Dermatologist visually diagnosed it as HSV (i dont agree) and put me on Anti-viral. Patch dried up and new patch appeared on back rib cage. Lasted two days, is dried up now. Not terribly itchy, no pain, no yellow crust, no genital or facial blisters... Ideas??