Oral sex would have never exposed you to HIV as there are at least 12 different substances in the saliva that neutralize the virus. The only ways HIV is spread are:
-Unprotected anal/vaginal penetrative sex.
-Sharing needles to inject drugs.
-Mother to child.
a 4th generation test is accurate 28 days after the exposure.
All the best.
Are you a male? A big tip off that he is not hetrosexual is that you were sexual with him . . . just saying. For oral sex though, you had no risk for HIV. The only risks for HIV are unprotected vaginal sex, unprotected anal sex or sharing IV drug needles. That's it. Saliva and air inactivate the virus. No one in the history of HIV has been infected from oral sex that has been documented or proven. You don't need a test at all for your encounter.
You don't need to test. RNA PCR wasn't necessary at all. As other members have stated, you were never at risk from your event.