It actually depends on your genetic makeup and what else is going on in your body - you’re more likely to catch something if your immune system is compromised already. The studies I’ve seen show that your chances of catching hiv are extremely low if you don’t have other active infections, parasites or lots of pollutants already stressing your body’s immune response.
one study showed that your chances are about one in a hundred of catching hiv each time you get bred if you never use protection and don’t already have a compromised immune system.
those of us who are fortunate enough to have inherited genetic resistance can still get it but at extremely low rates - basically the same as being on prep or using protection. I still suffer from survivors guilt having lost so many friends during the aids crisis and I think part of me wants to just get it so I can stop thinking about it at all.
the guys I let breed me say they’re clean and so far I’ve been able to avoid catching anything except crabs, a staph infection and cryptosporidium so I consider myself lucky.