Context: I had an exposure with a stranger, where I was the insertive partner (anal). After the exposure I panicked and started pep 5 hours post exposure. 

Everything was ok during the cycle, just lots of anxiety. My doctor told me to take a test at day 42 to have a conclusive result, since he told me that PEP does not delay a 4th gen HIV test (taken from the vein). But I’ve reading many different opinions that made me worry a lot. I took a full std panel at day 44, with all the results negative. But I don’t know if that test is really conclusive. My doctor and a teledoctor I paid for a second opinion told me that it is conclusive regardless of pep and I shouldn’t worry anymore and move on, but I want to confirm with you. 

PEP failures are so rare in persons who take their medications that estimates of PEP effectiveness are just that- estimates.  To place that in the context of your questions, let me point out:

1.  If you don't know your partner's status, no matter what risk group he was in, the is a far higher than 95% chance that he did not  have untreated HIV  (so on the basis of this fact alone, your chance of being exposed (not infected) was less than 1 in 20.  THEN.

2. With insertive anal intercourse, if your partner had untreated HIV, your risk for infection is less than 1 infection in 1000 sex acts (i.e. chances are better than 99.9% you would not b infected)., THEN'

 3. with PEP, assuming you took all of your medication, your risk for becoming infected is reduced by about another 90%

With these numbers, I'm sure you can see that PEP failures are rare- too rare to accurately do definitive clinical trials for provision of solid data (it would take enrollment of tens, if not hundreds of thousand of persons to provide such data).  Thus, I trust you'll see how hard it is to accurately predict when PEP has failed- its VERY< VERY rare.  That said, when pressed on the issue, most experts and public health organizations will tell you that a test 6 weeks following completion of PEP will provide definitive information although some experts then go on to recommend retesting again at 12 weeks, "just to be sure".  Certainly as implied by the comments from your own doctors, when person fail PEP, their tests are typically positive well before 6 weeks following completion of PEP.  

thus, this is a perhaps long-winded way of telling you that the likelihood that you acquired HIV is vanishingly rare given the data I've provided and presumptions I've made about your exposure.  Personally, were I you, I'd be completely confident in the results of your day 44 result and would move forward without concern.  Hope this helps. EWH

Regarding your more recent exposure.  The risk of this exposure is minuscule. Apparently you do not know the HIV status of your partner but statistically it is unlikely that he had HIV. Even if he did, receiving oral sex from an untreated, HIV infected partner has never been shown to put a person at risk for acquisition of HIV. There are a handful of cases in which HIV has been acquired by performing oral sex on an untreated, HIV infected partner however this risk is exceptionally low-only one out of more than 10,000 exposures is predicted to lead to infection. I would not worry. 

As you know, we provide up to three responses to each clients questions. This is my third response. This thread will be closed shortly.Take care. EWH