When the guy you have feelings for asks you for a threesome

He asked me if i have ever done a threesome. I said no. Then he asked me if i ever wanted to do one and i answer him yes. Why not. Having two men on both side of me would probably be awesome ;) then he replied saying no! The other way around with him and another girl. He asked me if I'm interested i just said no thank you! But to be honest I think i was more jealous. Would you do it? There is a possibility we might date. Especially since we were on that subject today. But i think i don't want to share him. Is it wrong of me to feel like that? He was just laughing when i kept saying no i asked him why he was laughing he just giggled and said nothing :/