Two possibilities:
I) Fling - no committment and don't expect any. We act like couple,
but doesn't mean we are.
II) Silent BGR - kinda childish in my context, but there are people
who resort to this because they couldn't say it from their mouth.
So they do what it seemed best - actions speaks louder than
words.
Before you ask him, look upon yourself. If you fall
under (I), there isn't a need to ask because its all in the spirt
of fun and free-will. You could ask as well and could be less tact
on your words, etc. In simple, you could chose not to bother too
much about your communication part. No promise made. No contract
written. Nothing stated. No words mentioned - So nothing
happened.
But if it is (II), you may like to resort similiar ways to
accommodate to his style - for example, when you go out with him,
SMS a message in your phone and show to him directly - asking him
what is your relationship with him like. Proceed from there.
P.S: In the first place, if you don't want to make things awkward,
weird or different from before - you shouldn't get involve with
someone that is in your class/group/etc because whether you
desire or not, you probably have to see him for a continuous period
of time. This could be a blessing, or a curse. 
Cheers
