Hi A guy called John.
I would like to say that I am no professional in the arts of counselling especially when it comes to relationships, however, I am more than happy to add to these comments which may be helpful.
First thing that you need to understand is that this is all about you. Let's go back 20 years, right before you met your wife.
Image that you're on a boat, sailing around the oceans and the seas and navigating all the most amazing islands.
Some are breathtaking, some are have big homes, some have little island shacks, some are ready to be tamed.
You dock at an island that you feel suited too and after you explore your island you attracted and are madly in love with it.
You work hard to build up your island, dedicating strength, time and commitment.
You start to wonder what other islands would be like so you get in your boat and you stumble across another island.
You start to commit to this new island and without knowing it, you have forgotten to look after your own island.
As you stand on someone else's island, you gaze over the ocean at what appears to be your neglected island.
Sometimes while we are going on in life, we forget about ourselves. We forget who we are and what were once before. Love is something you build, water, commit too and you want your island to flourish.
Anyway, this is just food for thought. You could start by ending your infidelity, focus on yourself, get out, get some hobbies make friends, get some counselling and learn the value of true inner happiness.
P.S. May be try the old spice up your relationship action and get that spark back, I mean you married your Woman why exactly?