My boyfriend wants to have a threeway kiss, and a threesome, am I not enough?

Well, we are still in highschool, and we’ve been together for a year pretty much, but all of a sudden he wants me to kiss other girls, and have a threeway kiss and/or a threesome, I explain to him how much that hurts me, but he still doesn’t seem to care, I can’t help but think, he doesn’t want me anymore. I thought the sex I was giving him was like great, but I guess, it really wasnt. I know its a dream for every man, but do you think he’s tired of me?