"I really don't consider my wife a nag, but I did feel pressure about the sex. For some reason, that's a turn off.
That's exactly what I was saying. My H didn't "consider" me a nag either, but my bringing the issue up, or talking about the need he wasn't meeting (no matter how gently I put it) had this same effect.
If you truly do have a libido that's dropped, AND you truly don't indulge in porn then I think a sex therapist is a good tool for you to utilize in figuring out this issue for you.
