No real words of wisdom here. Your post touched me and frightened me at the same time. I can easily see our current 6 weeks without sex piling up into months, then years.
I am familiar with the idea that something must be wrong with me. My communication of this line of thinking with my H has probably resulted in my seeming weak and unstable in his eyes and probably doesn't help his attraction to me. I am familiar with not wanting to have sex with someone who doesn't want sex with me and yet, desiring my H because I love him. It places me in a perpetual quandry. i have never seriously entertained the idea of an affair but I have entertained the idea of just giving in to my roomate marriage and having regular, planned solo sex instead of the usual mb due to desperation.
As I sit here I am thinking of you and have great sympathy for the position you are in. You will have to take some sort of drastic action in your M if you ever want the life you deserve. Nop is correct that there are times for ultimatums. Find strength where ever you can. I hope you have a church, a sister, a good friend, a therapist or all of the above to share this with.