Noun: First Dick Syndrome - A very common situation where a female has a false sense of affection for a male with whom she has had sex with for the first time. Most of the time, the emotions are stronger when the female lost her virginity to that guy. (Sadly, the feelings aren't mutual).
Guy 1: "Man, that girl keeps telling me that she loves me after we had sex the other day! I didn't even know she was a virgin!"
Guy 2: "And she's been calling you all week. Definitely sounds like a case of FDS bruh."