People are hating here but I am not judging. You should absolutely, absolutely have that serious talk with her, especially if you're at the point of thinking about cheating. I can't recommend enough that you have the talk before you cheat. Not after. Especially considering her past enthusiasm for sex, I think there's a good chance you might be surprised how she responds if you just tell her what you feel you're missing from your relationship.
I'll also say this. It is my belief that some people are intrinsically best cut out for monogamy, and other people are intrinsically best cut out for non-monogamy. Unfortunately, our culture essentially mandates monogamy as a required one-size-fits-all solution, especially in many religious communities. However, it just doesn't cut it for some people. I think of it almost as an orientation...some people will never be satisfied with monogamy, while others would be a disaster with anything other than a monogamous solution. It's all about what works best for the people in the relationship. I strongly believe this is a huge part of why so many people chronically cheat, get divorced, etc. (even when no DB is present).
If it were more socially acceptable for people to openly choose non-monogamy, I believe you'd have a lot less deceit, mistrust, sadness and unmet needs in the world.
I consider myself intrinsically poly so maybe I'm projecting onto you with this, but I do sympathize with these urges. You have a normal sex life, it sounds like you are just bored...people will point to that as a lack of maturity but I tend to read it more often as simply a different set of needs.
That said, integrity is everything in life. And you did make a vow to your wife. It's your responsibility to be honest with her, and if you want sex with others, renegotiate the terms of your understanding with her to an open marriage--or if she's not okay with that, choose to deal with the status quo or leave. Those are the only ethical choices. Take that with a grain of salt, and no judgment though, because I know that these things are easier said than done.