OK so from what I've observed (like a scientist or an anthopologist collecting data, analysising and nothing else) is that when it's with someone you see often (ie not just a randomer you hook up with) there's no such thing as a no strings attatched relationship.

There are fewer strings attatched relationships or different strings attatched relationships. And this is fine, so long as you know there are still some strings and don't get hurt when you trip up over them if it all goes tits up. And the difference between this and a 'normal' relationship is you might not always know what the strings are until you find one of you has got hurt.

Is he using you? Maybe. That doesn't necessarily mean he's doing something wrong and it doesn't necessarily mean he's after just one thing (shock horror! a college boy who wants sex, who'd have thought?).
He might be using you as a sort of transition girlfriend- he gets the emotional support, some- or maybe all, but it sounds more like you mean some- of the physical aspects, but knows it can't go that far because ultimately you're into different things.

Are you using him?
Doesn't pretty much everyone relationship involves people 'using' each other, that's almost the definition- you find someone to use for sex, or for comfort, or as a soulmate, or as a confidante, or a companion or all or some or any of these things.
The problem comes when one person things they're being used for one thing but the other is using them for something else- ie. they think they're a potential soulmate their partner just wants them for sex. Or vice versa. Or whatever.

Anyway, Dr Phil out. Enjoy yourself you free spirited college girl. Have fun!