InOneEar, I totally empathise about wondering if there's something wrong with 'me' (as in you yourself). If my experience is anything like yours, you might be wondering what is wrong with you, what a rotten person you are, what a rotten wife, if you could think these thoughts then what else are you capable of, etc. I think most people would say there's nothing wrong with you for thinking the thoughts, but if you act on them then that's a different matter. Problem is, the thoughts alone are so unfulfilling....
It would be much easier to deal with this and understand it if our OHs were not very nice, or if our relationships were on the rocks. But as OHs are great, and relationships great, what's causing this and where is it going to lead? Like many (happily) married women (and men) I'm sure, I wish I could just step into a parallel universe where I am single, to get this out of my system with no ill effects on my real married universe.
If you find a way to deal with, or get over, this, please let me know, as I need one!! (A few years ago I had an admirer, which was so flattering that it turned into a mini-crush on my part, and I did try to spend time with him, email etc - which had the great effect of making me realise just how much better off I was with hubby, so crush was quickly extinguished! But this wouldn't work in every case I guess.)