Roadlegs

Looking for a story about a couple, though I think it's largely about the woman. Pretty sure it's quite old, and I think it may have been a bit controversial. Dude is manipulative. I think the story opened up in medias res, with a scene in which the two are playing a fighting game, the girl obliviously messes herself, causing her to lose, then she begins to give him a blowjob or a handjob, though I think no details are given. Then we get exposition of how he'd slowly been making her diaper-dependent over the past couple of years, and how he's gotten her to view it as completely normal, even in public. No shame. I think I remember a couple of other scenes. One where she's locked/stuck in the guy's truck, or he's told her to stay put and she listens obediently, and she ends up wetting herself.