Homophobia is so rampant and insidious that it’s reasonable to fear your wife’s reaction to such a revelation about your sexuality, though it is unclear in your letter whether she has said or done anything to warrant such suspicion or if you’re just being extra careful. In a perfect world, your wife would accept your attraction to men as she does to other women (assuming that, in fact, you do have said attraction and she does accept it) but as we know, our world is teeming with rationale rooted in fallacy and assumption. In this case, that might require a bit of educating (Yes, wifey, there is bisexuality in men!).
I’m always a big believer in the straightforward route.