Since you don't use condoms at all, I would suggest a screening for all bacterial STD's:
Syphilis, Gonorrhea, Chlamydia, Trichomoniasis, UreaPlasma and MycoPlasma.
This rash of yours does seem to have some characteristics of herpes virus however... but if you want to be certain, I do suggest a full STD screening to see if this might be related.
Hi, rashes could be herpes but having outbreaks on the head is not common at all. They would be most often on the shaft or pubic mound area. Start off by having a blood test type specific for hsv 1 and 2. If 2 comes back positive they rash may in fact be herpes , it its negative you can rule it out.
Do you always use condoms during sex?