I'm actively going through something similar, but my situation is a bit more complicated (you can read my post about it if you want). Like you, I haven't been interested in anyone other than my spouse since I met him, until now. I can completely relate to your confusion because I feel the same way right now... I feel so guilty for thinking these thoughts because I feel like I'm betraying my husband, but on the other hand this has called into question whether or not I'm actually happy with him... It's a tough situation, for sure.