Cancerians - Emotional Insecurity?

When a Cancer girl is with a guy whom she deems is shady, should she just stop trying to make it work? Paranoid, emotionally-unstable, and quick mood-shifting Cancerian has always suspected that the guy is a liar and talks it up in order to mislead and hide 'hidden agendas' when it comes to certain subjects. ... Okay, the Cancerian is MOI. And Im just really insecure about the guy, always thinks hes lying and hiding things from me. Im very detail-oriented so I pay hefty attention to every factor of his communication to determine for myself if hes being true or not. And thus I get very, very sensitive about every little thing he says and does and especially the WAY he says it. I cant tell if Im just being insecure and overthinking just because I happen to be a Cancer and a woman OR am I that way because I am supposed to and my senses tell me something is REALLY wrong. I just cant trust the guy... I dont want to end it if it isnt the latter...cuz thatd just prove that we Cancerians are downrightcrazy b!tches.