I know where he is coming from because i was that guy. I use to get the horniest ever thinking of my wife with another man. When we first dated I convinced her to go fuck one of the guys she's been with before and leave her phone on so I could listen. It didn't hurt us. But now we are married and I want to watch it be done and she won't. Question is would you if he wanted you to with no consequences? I guarantee you will have the best sex in your life after you do. Also, if he wants u to when he is horny and doesn't want u to after he cums, that means he wants you to. That's the feeling I felt. And if you dont want to, go along woth him amd say you will until he drops the mood. Or make up a story that you did. Hope it helps!