Hello,   Typical STD tests do not test for herpes.  Two methods exist: swab the blisters and perform a culture for the virus, or draw blood to look for antibodies for the virus.  Either way, you'll have to have your healthcare provide perform the necessary test.  It could be a rash, like your doctor indicated, or it could be bacterial or fungal related, especially if you're uncircumcised.  Just because the woman is showing no signs of infection does not mean that she is in the clear.  Many people have herpes and do not know it due to very mild or nonexistent symptoms.  Get tested and put the wondering to bed.  Good luck...