Please, please, please.......these guys need to get some medical testing if it hasn't been done, e.g. testosterone levels, etc., in terms of low sexual desire, pre-mature ejaculation, or erectile dysfunction, before one assumes it's psychological or relationship issue. Lia, regardless of whether or not you're poly, I think your husband is being very selfish in refusing to go to a doctor. (I had the same problem with my ex-husband. I was so afraid to talk directly about it for fear it would make things worse, e.g. increased self-consciousness, but you've already taken that step.)
transcendental: I am shocked and disappointed that a sex therapist....especially one you saw for 2 years....wouldn't have INSISTED that possible medical/physical causation be ruled out before therapy progressed very far!!
Glad to hear you're going to someone different now!