Boyfriend?

So I've been with this guy for close to two years now, I'm 16 he's 18. Last month we had been at a party and gotten pretty drunk. When we got back to his place we were cuddling, about to go to sleep and out of the blue he asked if I would marry him some day. I was a little taken back by the question since in the two years we had never discussed a future together (because I don't like "what if" and neither does he so we just go with the flow) so I of course said I would marry him some day because that thought makes me warm and fuzzy inside. Now, a few days ago he brought it up again and asked what I was doing after graduation next year. So I don't know what's going on. If he's hinting at a future with me? Promise rings? Maybe ask me to move in with him after grad next year? What do you guys think because I certainly think these questions out of the blue about a future with me are a strange behavior from him. Am I over thinking things?