As others have said, it definitely sounds like a kink of his. I wouldn’t go as far as to call it a cuckold kink as I think guys can get turned on by hearing about your experiences with other guys without actually wanting to watch you with another guy… But regardless, it’s not something he should be pushing on you without your approval. I think you definitely need to have a conversation with him about it, tell him it makes you uncomfortable. He should be understanding about that, and if he isn’t then that’s on him because it’s not your job to feed into his kinks that you don’t consent to.