Thank you for having such a wonderful platform for anxious persons like to seek professional advice.

Today I had sex with a high-end CSW(500USD/h) who says she gets check-ups every half a year.

I wore the condom when I was not fully erected. And when I got erected, we processed to sex. I guess at that time the condom did not cover all my penis. Since she was above me, I was not able to see whether the condom covered all the way to my shaft or not. The sex lasted ~ 2 minutes. After I ejaculated, I tried to move out my penis slowly. However, I realized when I moved my penis out, the condom was not on my penis. It is probably because I had lots of pre-cum and made it very slippery. The CSW told me that the condom stayed in her body and she tried to hold it while I pulled out so that the semen did not go out. Later on, I checked the condom and I am very confident my ejaculate was in the condom. 

In this case, I guess I am just not very confident whether condom was covering my penis or not, although I am confident that the ejaculate was in the condom after the sex. 

In my situation, do I need PEP? I am fine with any side effects if it helps....

Thanks!

If your condom remained inside your partners vagina is you with drew, it likely did it’s job reducing your risk not only for HIV but for other STI’s as well. When condoms come off the penis during sex they typically are pushed deep into the vagina and there is no question that they are off. Your situation does not sound like that. I would have a little concerned about HIV and I certainly would not recommend PrEP for an exposure such as the one you discuss.  EWH 

Since I do have a change to follow-up questions, I would like to ask for your thoughts/experiences. I, myself, is a scientist, without deep HIV-specific knowledge. Since you are here, can you comment on the effectiveness of HIV treatment when someone has access to medical care? I guess what I am trying to ask is: have you seen anyone infected, who follows the doctor's advice, takes ART daily as prescribed, and takes CF4+ counts periodically, but still fails to remain an undetectable level? How exactly effective is ART treatment for patients who have the access and resources in US?

Regarding your follow-up question and the effectiveness of therapy for HIV, there may be occasional persons infected with a resistant strain who progress despite treatment however this is very rare. For persons who are diagnosed relatively early in the course of the disease (within a few years of acquisition) and adhere to their medication prescriptions, HIV therapy has transformed the infection from a death sentence to a chronic illness requiring daily medication.

EWH 

Your statement made in your follow on comment is also correct. If the condom had come off and failed to cover the head of your penis it would’ve been pushed deep into the vagina and not been easily removed. Furthermore when you ejaculated the ejaculate would not have been in the condom. All of this is evidence that the condom was in place and came off as you were withdrawing from your partner. 

I hope this information has been helpful to you. This completes this thread. Take care. EWH