Sorry you're dealing with this. I've been with someone who doesn't orgasm and is somewhat frigid. It's very painful, soul crushing really. Yeah no duh you want an affair, you're only human.

If your wife doesn't masturbate then you are really screwed. Only 20% of women are capable of orgasming from penetration, meaning most of us get off by "rubbing one out" with out hand or grinding on a guy. As a girl you figure out how to do this by masturbating, so it will take her loads of self exploration IMO to even have a shot. Unless... You have lesbian esque cunnilingus skills.

Unfortunately I have no advice, but it's not your fault. I've been there too. I've wanted to cheat. Don't know what to say other than, how human it is to want to be intimate...