Sexistential Angst
Post-hook up worry about things being weird because you hooked up with that person. Feeling bad because you had sex that might not have been a good idea.
"I just did one of my ex's friends and am now suffering from sexistential angst."
"I've got some pretty bad sexistential angst, wondering how long I should wait before I call this dude."
"I've got some pretty bad sexistential angst, wondering how long I should wait before I call this dude."