I'm searching for a story I stumbled across but lost track of. It's from the guy's pov. He has some kinks, including chastity and diapers. His SO isn't super in to them herself, but accomodates him. They have a rule where he can put on his cage and or a diaper whenever he wants, but if he does, he is in them until she decides to let him out. if they get frisky while he's locked up, she'll typically tease him a bit, but then unlock him and they'll do the deed. This time is different, though. Instead, she says that just because he's locked up doesn't mean she shouldn't be able to get off. She has him put on a strap on so she can have her fun, but he is denied. The story spends some time describing what he goes through, lusting after her, yearning for release while watching her get her own, seeing the familiar sight of her bouncing on is hips but not feeling anything other than the dull pressure on his pelvis. I don't remember where I was this story, but I'd really like to find it again.