I think it's really a sign of an incredibly mature mind that you are content with who you are and equally accepting of your wife's identity. It's something that is much easier said then done.
That said, it doesn't mean you're a robot and don't have moments of doubt, insecurity and fear. It goes with the territory. Feeling that maybe someone might come along and out-compete you for her attentions is natural. Knowing that doesn't make the fear go away, but it does allow you to compartmentalise those feelings so that you can get on with your life. I think that your wife probably has a very different view of the situation, she might just think she's the luckiest woman in the world to have someone that not only loves her, but accepts her for who she is. Male or female, that's a rare thing.
Take the risk of thinking for yourself, much more happiness, truth, beauty, and wisdom will come to you that way. - C. Hitchens
Me: Male, bi, 48, flexible