I've had this side effect before, I think it was with effexor, but honestly I've been on so many I don't remember which. It was terrible. It caused great problems in my marriage (as far as our sexual relationship) because my sweet husband felt like he was failing me somehow.

I would mention it to your pdoc if you can. I was always way too nervous about that to dare mention it, but I eventually quit taking effexor cold turkey after deciding I didn't need meds anymore. (Ya, that wasn't one of my best moments, but I learned from it.)