Ok, so I am engaged, and for the last 3 years, my relationship has been happy and healthy. We had sex almost every day, sometime multiple times a day, But ever since my fiancee and I had our child, our sex life has almost diminished. I hardly get turned on anymore, and I find it tiresome to even attempt at sex.

Lately, though, I have been hanging around my fiancee's cousin, and I find myself more and more attracted to him as time goes by. Its evolved into a sort of crush, but not in a long term relationship kind of way (he is married) but just in a sexual way. I even find myself getting turned on by him (something that doesn't happen much anymore)!
However, I'm not quite sure how to approach the whole thing...