Most Helpful Girl
It sounds like a game to me.
It sounds like he's having a good laugh with your ex behind your back over the fact that you're gullible and think he wants to go to prom in 7 months with you and loves you. That is WAY too fast to honestly say that kind of stuff, which is why it makes me think it's a joke.
I think you should break up with him after having a conversation with him.