I have a rash and itching in my groin that spread to my testicles and now my butt crack. No discharge from my penis is present. Could this be a STI?A girl had given me oral sex. On another note I had sex with my wife who had a vaginal fungus. Could any of these be related?

I'm sorry you felt the need to return to the Forum.  The rash you describe in no way suggests an STI.  Sixteen days ago, for what sounds like the same rash, I replied " The rash you describe does not suggest any STI. What you describe may be a fungal skin infection, which would be unrelated to the encounter you’ve described, but could be related to chaffing related to your recent extensive walking."  This may be the same fungus that is troubling your wife.  Receipt of oral sex would not cause a rash of this sort.  EWH---