Wow.
Well, as I read through your post, my thoughts refelcted, for the most part, those of others who have responded. That is, until I read your little throw-away statement that, imagining being with guys, "stirrs more emotion from me."
OK, so at 23, having had moderate sexual experience with women and minimal with men, I considered myself a bisexual. I could respond and function sexually with either sex and was spending WAY too much time trying to convince myself that this was, after all, the best and most natural of sexual orientations. Actually I was an absolutely "confus-ed" sexual and once I realized that while I was an equal opporunity copulator, my emotional response was to men, my path cleared and I began the journey to self-acceptance as a Gay man. Granted, I was single and had not spawned.
I don't share the opinion that this can be handled lile any other extra-marital attraction, but regardless, I do believe that you need to share whatever it is you're going through with your spouse. Over the last 30 years, I have known couples in this situation who have chosen to stay together, living separate sexual lives and I have known couples that split. But in both instances, they had the maturity to work it out, realizing their responsibility to and for their children and now, with enough time passed to evaluate, they did a good job.
You're so young! It won't be easy, but it most likely won't just "go away," and will only get more difficult and damaging to all concerned the longer it stays hidden. So there it is, an opinion - a judgement even. Well, I'm old