Ours became a SSM. I was bitter that he only seemed to be interested in my body and had less and less desire to be physical with him. The meds I was taking to help me sleep through the night did not help with my libido.
I went through a sort of MLC in my early thirties when I saw that I was trapped in a very unhappy marriage. I never had an affair, physical or emotional; I just started feeling very unfulfilled and disappointed by how my life had turned out. And I guess the action in the bedroom just totally dried up.
This is likely very typical of a man. A sexual pursurer and emotional distancer.