Only sex risks are unprotected penetrating anal or vaginal which you didn't have, so there was no need to test for HIV. Your doctor doesn't seem to know about HIV or perhaps he just wanted to be cautious in case you didn't remember all your sexual episodes so he tested you. Anyway, you don't have HIV and don't even need to worry about it or do a 28 day test.
Everyone posts here about their supposed ARS but I have never seen anyone with ARS, chiefly because they had no risk as is the situation with you. So relax about HIV.
Likely your doc is correct with this below diagnosis, so continue to work with him. " my doc .... told me it could be exanthem rashes."
Good luck.