Go to a Dermatologist. You don't have to tell them what you're growing. I developed a "rash" (and thats putting it mildly) shortly after I started growing. I thought it was the MH lights (They put out mad amounts of UVA), the nutes, I was using chems at the time, my dog, everything except what it was. Turns out I had atopic dermatitis (shingles). It's from the varicella zoster virus (chicken pox). It seems that when you get over the chicken pox, the virus goes dormant in your nerve endings. For the vast majority of us, thats the end of it. But for a few of us, it comes back in the form of little bumps that will drive you nuts with itching. I now get a prednisone shot about every 2 months or so. The relief was incredible.
Not saying thats what it is, but ya never know...