At 33 I've already experienced the loss of libido, in my case it was our sex drives didn't match so I became frustrated, expecting to be told I'm tired, not feeling well or its my time of the month. Eventually I just stopped trying. What helped somewhat was reading and applying the tips from this article: Webmd

I agree with the others that looking outside of the marriage is a recipe for trouble. You have said that you've never participated in any of the kink before, Why not have a conversation were you ask about her fantasies and how you can help make them real. Open up about your own fantasies and see if she would be willing to fulfill any of them.