specific magical binding fic

[birdclaim]

Hi! I'm looking for a specific fic where I don't know how but Arthur and Merlin become physically bonded. So every time one gets aroused so does the other one. It's in Merlins pov and Arthur is getting more and more frustrated. I remember Merlin just getting off like once a week or something because he's avoiding it. I read it a long time ago so I may have gotten things wrong.

Any help is appreciated thanks!!