so I ended up sleeping with this guy from a dating app hes positive claims hes undetectable we didnt use a condom.. I was the (Top) and he was the bottom Im still on prep what are my chances Will I be fine ? I asked him if hes undetectable he told me yes ... and I told him Im on prep he said for me not to worry ... I wanna say I believe him cause hes open about his status ... I only topped him Im just scared about it but. I been on prep for a year already Im just freaking out and cant stop thinking about it .... Im having a Huge Fear over this ...
Congratulations on allowing yourself the experience of a pleasurable sexual connection with another person. It saddens me when anal sex is followed by so much fear and worry, especially in light of the proven biomedical prevention options you are both utilizing so well. Let's make sure you are clear on what those options are all about.
PrEP is taken by a person who is HIV negative in order to protect themselves from detectable HIV viral loads. PrEP has been studied and prescribed for more than 11 years now and is seen to bring down risk of acquiring HIV to nearly zero. At the time of this writing, there are more than 380,000 people using PrEP in the world, and only three instances of someone acquiring HIV with verified adherence to PrEP (http://www.thebody.com/content/80972/has-anyone-gotten-hiv-when-they-were-on-prep.html). That means if you have been taking PrEP as prescribed for over a year now that you have a near zero chance of becoming HIV positive, even if your partner were detectable.
However, your partner has told you he is undetectable, and seemingly has no reason to inaccurately misrepresent his status, nor deceive you in anyway. When someone has an undetectable viral load for six months or longer, they are considered "untransmittable," meaning they can't sexually transmit HIV to others (https://www.preventionaccess.org/).
So we can see here that there is no way HIV could be transmitted in the scenario you described. You being on PrEP means it nearly impossible to acquire HIV. His being undetectable makes it completely impossible for him to transmit HIV.
Then, if you add in the additional prevention strategy of "strategic positioning," i.e, topping as a way of reducing HIV risk, we can see that it makes the zero possibility of you getting HIV here about 90% less, which is still zero. So even if you didn't have PrEP here, and even if he was detectable, your risk of acquiring HIV from topping would still be less than 1% (https://www.poz.com/article/HIV-risk-25382-5829).
Put this all together, and I'd say you have no reason to fear acquiring HIV here. But of course, my words are not going to be as convincing as an HIV test. Given you're on PrEP you are probably getting tested for HIV about every 3-4 months anyway. Once you see those negative responses on a lab result I'd encourage to use medicine and science to guide your sexual decisions, and allow yourself the pleasure of merging your body inside another person if that's what you wish to do.