Sounds familiar. I can tell you that one thing that got me into the pattern was the constant rejection, overtly and indirectly. My wife has a habit of telegraphing the "I'm tired/stressed/too fat/too hungry/preoccupied" etc so I just gave up.
Let's say I ask. I may not be terribly randy, but could do it IF my wife was into it. What usually happens is she may acquiesce, but will be detached and not that into what's going on. The partner picks up on this. I do, and I know lots of other spouses do too. That's the unwanted side effect of "just do it" IMO. If I was an insensitive dolt, I wouldn't care and I'd just use my wife as a pincushion and be a happy dude. I just expect this to be mutually pleasurable, if it's not I'm not going there. Too creepy.
If none of this applies to your sitch, then I'm not much help.
