From your description of the rash
& the history of 'protected' sex, it does appear unrelated to any STD as such. Yes the shaving was possibly the factor implicated. It is what we commonly term a 'pseudofolliculitis'. It arises due to ingrown hair & due to a staphylococcus infection
or other bacterial infection, may have spread to contiguous hair follicles. Dont worry about any STD's. Use a topical antibiotic-corticosteroid ointment for 3-5 days & stop. Use a systemic antibiotic of choice for 5 days eg doxycycline hydrochloride 100mg twice/day & all should be well. Avoid shaving against the grain in future & perhaps go in for laser hair removal
to rid yourself of unwanted hair. I have such laser machines' et al in my clinic in Bangalore & will be happy to advice further should you wish to get in touch with me directly or through the 'ask-a-doctor' premier package. Cheers & Good Luck!
Dr Praveen Rodrigues MD
, Cosmetologist, Venereologist