My husband wants to watch me with another man. Im wrecked trying to make sense of it

A month ago after a couple of glasses of red, he told me he has a fantasy. He wants to watch me with another man. Not join, not swap with another couple, just watch. I laughed at first thinking he was messing. He wasnt. Said hes been thinking about it for two years but was terrified to say in case I thought he found me disgusting. Im 35, married ten years, two kids, living in Drumcondra. Always thought our sex life was fine. Bit slow some weeks, on fire others, nothing unusual. Im three weeks in my own head with it now. Part of me is mortified, part curious, part flattered that he wants me badly enough to imagine sharing that view. Im scared though that after it happens he sees me differently. And scared he wants to keep doing it and I wont. Anyone whose partner brought up the cuckold fantasy — what came next? Did it bring you closer or eat at you slowly? And how do you tell the difference between a real desire and a one-off wine-fuelled idea?