The bottom line (pun not intended, but there it is!) is that you do not have HIV.

Had you asked earlier, I would have advised completing the prescribed 4 weeks of PEP. There are no data on its effectiveness with shorter courses, like 20 days. I don't understand what you mean by "descovy by itself is just a PrEP". It makes no difference that the same drug is used for both PEP and PrEP; this didn't mean you could safely stop PEP early. However, your negative test results are conclusive since you tested negative more than 6 weeks after your last dose. Some experts believe that if PEP fails it might take up to 3 months for testing to become positive, but almost certainly 6 weeks is plenty. However, because of that slight uncertainty it is reasonable to retest as you plan, i.e. another AgAb (4th generation) blood test 90 days after the last dose. It will also be negative.

In addition, your negative test results prove your symptoms are not due to HIV. The symptoms of ARS are not caused by the virus itself, but by the immune response to it -- and antibody is part of the immune response. Therefore, with symptoms caused by HIV, the antibody tests always are positive, no exceptions -- no matter how long after exposure the symptoms are.

If your symptoms continue and/or you remain concerned about them, follow up with your doctor. But you can put aside any worries about HIV.

However, I do hope this has been a learning experience for you. Please use condoms for future anal sex events, or take PrEP; and also discuss HIV status before having sex with new or casual partners. Most people are happy to have such discussions -- and to not proceed with partners who are positive and not on treatment, or who seem evasive in their replies.

I hope these comments are helpful. Let me know if anything isn't clear.

HHH, MD

That said, we don't really know that 4 weeks is truly necessary for effective prevention with PEP; 20 days may be fine. It is almost impossible to study the actual effect of PEP in humans, and even animal models -- i.e. with primates -- are extremely expensive and impractical. Most likely 20 days is fine -- and it wasn't such a bad idea to cut it short if the side effects were bothersome.

No STD other than HIV causes symptoms like you describe, and assuming you had the proper kinds of STD tests at the 20 day mark -- chlamydia/gonorrhea testing by urine or urethral swab, rectal swab, and oral swab if you have recently performed oral on partners -- you can be sure you don't have those infections. It was a bit soon for syphilis testing; around half of all newly infected people would have positive blood tests at 3 weeks, so you should have another test 6+ weeks after the exposure (90 days would be fine). Don't test for anything else:  all others are too unlikely or the tests are not reliable. Still see a doctor if your symptoms continue, but almost certainly they are entirely unrelated to the sexual exposure described above.

I do hope the discussion has been helpful. Best wishes and stay safe.