I've heard of stories from friends that hiv contraction is largely about luck. "YOU CAN HAVE FULLY PROTECTED SEX ie from the start to end with proper condom use and still end up sick" they say. Is it true?
Does washing up immediately after sex matter? Ive read a journal that said it increases the risk of contraction especially for uncircumcised men.
If Vaginal fluids came into contact with urethra opening doesn't posse a risk?
Your questions bring up pertinent issues, especially when it comes to stories friends tell each other and how we determine if anecdotal information is factual or not. What your friends are telling you do contain nuggets of truth, but with a big "BUT..." attached.
(1) "HIV contradiction is largely due to luck." Based on the numbers there is some truth to this, as the chance of getting HIV in most scenarios is really quite low (https://www.poz.com/article/HIV-risk-25382-5829). BUT...one can certainly reduce or eliminate those odds by practicing safer sex which may include using PrEP, condoms, having sex with an HIV+ partner who is undetectable, being the insertive partner ("top") or any combination of these strategies.
(2) You can have fully protected sex and still get HIV [notice I did not use the word 'sick' here, given most people living with HIV or STIs are not 'sick']. This one is tricky, given how little we know about how well condoms protect from HIV. What we do know is that HIV is spread through semen, blood, or vaginal fluids. If a latex barrier prevents one of those bodily fluids from entering directly inside another human, then the condom worked, and one can not get HIV without these fluids. BUT...condoms are problematic for many because they often reduce pleasure and sensation, psychologically provide a barrier to intimacy, can break, and must be used correctly in the heat of the moment to work (at a time our brains are often least rational).
(3) There is one study that suggests that uncircumcised men who washed their penis after sex had increased risk of acquiring HIV (https://www.nytimes.com/2007/08/21/health/21hiv.html). BUT...this was only one study that looked at men washing after vaginal sex. They did not establish the definition of "wash," meaning it is unclear if they used water only, water and soap, if this made any difference at all. They did not apparently ask about rectal sex, so we don't know if vaginal secretions or rectal secretions would make any difference. And finally, this study hasn't been duplicated or validated in the 11 years since it came out. What we do know is that PrEP eliminates risk of acquiring to HIV to nearly zero when used as prescribed, whether someone is circumcised or not, whether they are having vaginal sex or rectal sex (http://www.thebody.com/index/treat/tenofovir_prevention.html).
(4) Vaginal fluids can contain HIV and can transmit HIV to a male partner through his urethra. BUT...the HIV must be detectable, meaning there must be a viral load. Someone living with HIV who is undetectable for six months or longer cannot transmit HIV to another person (http://www.thebody.com/content/80813/hiv-undetectable--untransmittable-uu-fact-sheet.html?ic=7001). And even without undetectable status, the risk of vaginal-penal HIV transmission is quite low, less than 1% (https://www.poz.com/article/HIV-risk-25382-5829).
I hope these answers help you to consider what the best choices are for you and your partners. When in doubt about stories or rumours from your friends, please feel free to ask us there at TheBody.com, and/or join the global "PrEP Facts" community on Facebook at: https://www.facebook.com/groups/PrEPFacts/.