HIV is unable to reproduce outside its living host (unlike many bacteria or fungi, which may do so under suitable conditions), except under laboratory conditions; therefore, it does not spread or maintain infectiousness outside its host.
HIV is transmitted by;
Unprotected penetrative anal and/or vaginal sex
Sharing works with other IV drug users
Mother to child
Sorry, just to double check (Which I know you get a lot)
But in no way can semen enter the body this way, whether it being through urethra or the penis head's mucus membrane?
Thanks again, and sorry to bother you.
You're being paranoid, HIV is not transmitted by masturbation.