Would you be happy with this? Sex once a month or so but only if you instigate/make an issue of it? Duty shag if you will?
How about if you knew when you were in bed alone, your DH was downstairs looking up terms such as "milf" and "naked Snapchat"?
How about if you knew your DH had no trouble getting/maintaining an erection, he just couldn't be arsed to use it on you?
And yes, I've spoken to him. He denies there is any problem.