Nice to have you here(Sorry) Currently in a sister/brother emotionally detached relationship, within a 23 year SSM, I share your pain.
I was pleased to find the antidepressant; Celexa, taken for seasonal affective disorder has dampened my libido, to the point where I have decided to remain celibate. I have given up on ever having a intimate, sex life with my wife, opting to give up all the anger and frustration that goes along with this lack of intimacy and sex, for a more tolerable celibate relationship. I've taken some heat for this, with others that post here, but it is working with me. You too, will find your "happy medium".