I'm an old poster and not about much more (have namechanged for privacy) but had to comment as very moved by the discussion - this was completely my situation 10 years ago and I could have written so many of these posts word for word.
My ex-H began rejecting me sexually after the first six months we were together. For the next 18 months we had only sporadic sexual contact, usually consisting of quick pleasure just for him. I stopped making advances after awhile of this as the rejection was so humiliating. Both my ex-H and I were in our 20's. I was considered attractive and had never been short of boyfriends or interested men. I had never experienced anything of the sort, and was extremely hurt and confused by it all.
It was absolutely soul destroying, and looking back I can't believe that I endured it for the six long years that I did. The worst thing, more so than the humiliation of constant rejection, was ex-H's complete refusal to discuss the issue. Every time it was brought up, I was met with rage. We would argue and he would storm out and be cold for days. I found it heartbreaking that the person I loved and cherished so much didn't want me in the same way I wanted him. At all. And also, how he didn't particularly seem to care how hurt I felt by it all.
After 4 years of no sexual contact al all, I snapped and had a number of affairs. I'm not particularly proud of that but I was very depressed and hardly in my right mind. I never lied outright to my ex about any of this, we had more of a "don't ask don't tell" arrangement. I wasn't brave enough to simply leave. Despite the complete lack of physical intimacy, we were very emotionally entangled, plus I was living in a country that was foreign to us both, and my work and housing situation was quite unstable.
None of these relationships were serious until the last one when I fell in love with my current DH and left my ex for him. I wasn't brave enough to leave my ex before this moment of realising that I could actually spend my life with someone who truly loved me - body and soul. My self-esteem was zero at the time, so it was a complete revelation to me.
I never found out what ex-H's problem was - young man, not gay, not abused, no ED, low T or anything like that. I think that after the initial phase of our relationship, he just stopped fancying me (though he always said that he still did, strangely enough) but was too weak to end the relationship because of the emotional comfort it provided.
FWIW my DH that I've been with now is a wonderful, caring and attentive lover. We have been together for 10 years, and have two young DC. We couldn't be happier, and I feel very fortunate to have found such a good man as I've found in him. We have sex maybe 2 times per week on average - we would both like more but are sometimes too worn out - DC are 1 and 4 and neither have been great sleepers though the eldest has made a lot of improvement over the past year. Besides, the quality is so good when we do that the quantity doesn't matter that much. For me, I like sex not so much to scratch an itch but to give and receive pleasure with the man that I love.
Weight / aging / misogynist argument does not apply in this case. I was with ex-H from age 22-28 and was a size 10. We had no DC together. I am now 38, a size 14 and have had two children. I look after myself and my body, but I have fine lines on my face, stretch marks, a bit of cellulite, section scar from DC2, I bf DC1 until age 2 and am still bf DC2. DH says I grow more beautiful every day.
My heart goes out to all of you in this horrid situation, it is utterly soul destroying. I truly hope that you can find a way out cause it's hell.