Hey Misty. Sorry to hear about your situation and glad you found your way here. Given you are here and picking up a copy of MWDs books, I'd expect you're interested in divorce-busting. So, starting a relationship with another man sounds inconsistent with DBing to me. It stinks that your H is seeing someone else. As the saying goes though, the problem with trading an eye for an eye is that both people end up blind. Two wrongs don't make a right. Pick your cliche.
Put in DB terms, how would you having an affair, or event starting an emotional enmeshment with this other man, serve you in terms of goals associated with particpating in a divorce-busting forum?It feels to me like trying to hedge your gets by building up a side relationship while waiting to see where your M is going. If your kids were old enough to understand, how might they look at what you're proposing to do?
I say this because going through my own process, I've had women hit on me when out on my own, ex-girlfriends resurface at events with mutual friends, etc. and the best guide for me has been "what would my daughter think"? As much as an ego stroke as it can be to have someone attracted to you, giving in to cheating (at any level) is the cheap and easy thing to do IMHO.
Psychologically we need time to recover from whatever occurs in our current marital relationship. Introducing another "third" into the two person relationship between a H and W just muddies the already conflict-filled water. This process takes patience, lots of patience, if your goal really is to bust a divorce. Perhaps that not really what you want do and that is 100% fine (to decide to move on). If you're not already doing so, i'd encourage you to find a good therapist to hash things out with to discern where you're really at with saving your marriage or not. It might help you figure out more quickly where best to put your energy....for your own benefit and the benefit of your kids. Just my opinion and you know what they say about opinions!