Ponty, you are apparently confused between fantasy and reality. Your wife, your marriage - that's reality. Your illicit affair, that's fantasy. Sorry, I must be blunt. That relationship has no weight to it, no challenges. The most challenging thing about it is making sure no-one finds out, but that's also part of the thrill, isn't it.
So, you're bored. So is she, obviously. Your wife doesn't thrill you anymore. Hey, welcome to life. Maybe you're thinking "Is this all there is?" Well, only if you let it be, but unless you have WORKED tirelessly, for at least as long as you've already been married, to salvage your relationship with your wife, and can honestly look at yourself in the mirror and say "I have done all I can," then you have NOT earned your way out of that marriage. And the time factor doubles (at least) if there are children involved. You owe this not only to your wife, but also to yourself. You need to realize that unless you can conduct yourself with integrity, you won't be able to respect yourself, and that is ultimately the most important thing.
You have chosen to post this in an area where pretty much everyone is ABOUT respect, integrity, and being true to themselves. You can do no less.