I was watching a youtube video of a private investigator reviewing movies and tv shows, and in a movie a female character says "A wife always knows". The investigator says she is spot on, that "women know". They keep the numbers every year, all over the globe, and 96-99% of the women who hire them are right. Men are about 50%. He attributes this to men being more wary of other men.

If you suspect something - back yourself. If you think he's cheating, if he's overprotective of his devices, throw him out. Follow your intuition, she is smart.