Yes, need ka muna magpatest before getting HIV Prep. Pag negats ka, you get Prep. Pag positive ka, you need ARV.
Doxy? As Doxypep? After bembang to tinetake, to try and prevent syphilis, chlamydia, and gonorrhea.
Remember:
PEP - post exposure prophylaxis - Post means after. Meds taken after a potential risk (ie HIV, Rabies, etc - diff disease = diff meds ofcourse).
PrEP - pre-exposure prophylaxis - Pre means before. Meds taken before a potential risk. (ie: Rabies Vaccines, Truvada for HIV, etc)