I had an encounter with another guy of unkonwn status. I was the insertive and used condom during all the intercourse. The condom did not break ( I checked it after having sex) but I found out that during the intercourse the condom was partially slipped ( like 2.5 cm from the base of the shaft). Given that scenario, there would be an extra risk for hiv transmission ( from the bottom to the top).
Thank you for your inquiry. From what we gather from the question, you were asking about the possibility of (additional) risk of HIV transmission, in the event that the condom you were using during insertive/penetrative sex had slipped.
It is important to acknowledge that you were responsible in using a condom for penetrative sex, as condoms can act as a significant barrier for protecting one's self or partner from HIV transmission, aside from other biomedical methods such as (Treatment as Prevention/PrEP).
HIV transmission incidence is known to be reduced by approximately 80% with the use of condoms during all acts of penetrative vaginal sex (1). However, they do not reduce the risk of transmission of HIV to zero. Further, information provided by the CDC exclaims that "Latex or polyurethane male condoms are highly effective in preventing HIV and certain other STDs when used correctly from start to finish for each act of anal sex. People who report using condoms consistently reduced their risk of getting HIV through insertive anal sex with an HIV-positive partner, on average, by 63%, and receptive anal sex with an HIV-positive partner, on average, by 72%" (2).
Penetrative sex that is protected, despite the scenario you have described above, is what we would consider a Low Risk activity (Evidence of transmission occurs through these activities when certain conditions are met). The reason that we would consider this to be Low Risk is due to the lack of 100% certainty of condom protection, and the possibility of condom misuse. The event you described does fit into the category of condom misuse, although doesn't technically appear to warrant a High Risk (There is evidence of transmission through these activities and are the majority of cases of transmission).
Our Recommendation would be to routinely seek HIV screening if you are continually engaging in Low Risk activities, even with condom use. Knowing ones HIV status is the first step to eliminating risk of transmission to others and yourself.
All the best,
AIDS Vancouver Online/Helpline, Cody