A natural feeling experienced by beta men when they know that they are dating a female that has been much more promiscuous than them. It often leads to break ups when the beta male can't deal with his girlfriend's past and loses the desire to commit to her.
beta 1: How are you and Suzie?
beta 2: Slut angst kicked in hardcore, so we broke up.
(now less) beta 1: It happens. Let's go try to sleep with these promiscuous women instead of investing in them!