Beau, welcome aboard this leaky boat. You do belong here. I'm not married either (have no plans to be, but live with my bf of three years). Suggest you start your own thread below and others will join in the discussion.
If you've been reading this board for a while, you will see that most of the participants have been married for many years and have been struggling with this issue for a long time.
Be prepared to have the long-time-marrieds ask you why you plan to marry this person when you already know you are incompatible in this important area. I know, we keep hoping things will improve.
I don't care for your therapist's implication that there's something wrong with you wanting to share sexual passion with your partner. But the point is well made-- maybe each of you would be happier in the long run with someone whose sexual needs were a better match.