What Causes Whole Body Rashes Which Are Spreading?

Hi, I recently noticed some rashes starting to appear all over my body. The first sign was on my penis. Wasnt that big of a deal. then it started spreading. Went to the doctors, got tested and they found nothing. I talk to my aunt, shes an RN ( by the time i talk to her the rash was in small areas on my arms hands thighs) and she told me to use cortisone and i should be fine. I used it on my penis and within 3 days i was fine. Im starting to see more small clusters on my body. 3 on my right arm 2 in my right hand. 1 on my wrist. Also my GF started getting them as well.... do you know what this might be?