I have been in a dark room in a gay club, where people engage in oral sex, four times in the past. Each time, I received oral sex for about a minute (did not give it). I believe in some cases, the guy giving me a blowjob had only seconds before given someone else a blowjob, and possibly he had traces of the other person's cum in his mouth. I read there are next to no reported cases of HIV being transmitted by receiving a blow job, you say 0.5 in 10000. But how much higher is the risk in my situation, where there may have been another man's precum or cum in the mouth of the person giving me the blowjob? Would the saliva have diluted the other man's cum too much to infect me via my penis or foreskin?