Threesome?

so I'm 17 yr old junior in high school and since July I've been hooking up with a college boy who recently turned 18 that graduated from my school. he usually comes back home and goes to football games on Friday nights at my school. Friday, he brought some of his college friends with him to the game, and I went also. I walked past him and we smiled at each other but then he texted me. he said "hey would you be interested in a threesome with someone?". I told him I didn't want to but he kept bugging me about it and saying he wanted to. then later that night he said he was just joking around. I don't know if he really was joking or just said that cause I told him no. What do you think? Also, have you ever been in a threesome, and how was it? Because I have been thinking about it lol