Most Helpful Guy
If you don't want a boyfriend then that's your choice, tell him that it was just a one night thing, it's not your fault if he wants something more
Most Helpful Girl
If he is giving you mixed signals, it's time for you to give him a very clear one.
Men are very visual creatures. This means they may not always see the social nuances behind a woman's actions and misinterpret their intentions. This also happens to be why men so often see interest where there is none. Women are less visually stimulated but more mentally stimulated, so they may pick up on subliminal cues but not the obvious and intentional ones.
His "not so subtle" intentions seem pretty clear. He can't get over the idea that you aren't actually his, even if you've never discussed that as a possibility. For a small portion of guys, they think that if they have sex with a woman they "own" her in some way. This isn't always malicious, but it does grant them a sense of entitlement. He might feel like he deserves your affection and attention.
If that's not what you're looking for right now then you need to give him a very clear message, not simply let him continue to delude himself.