Fiancé saying he wants another girl for pleasure

Hey everyone,

Myself and my fiancé have sex about once, twice a week. Recently he’s been doing dirty talk whilst we’re having sex which to some extent it does turn me on. The last 2 times we’ve done it he’s suddenly mentioned about a girl going ‘down’ on me and that it would turn him on and he’d love to see it. I don’t know how I feel about it as it was a Massive surprise and this has never been mentioned before (8yrs of being together) this is something I now can’t stop thinking about and want some advice and if anyone else has had the same thing??? I’ve tried talking to him about it but he seems to dismiss it whether he feels uncomfortable I don’t know 🤷🏻‍♀️