Your period might be late for a lot of different reasons--I know when I was on the pill, I'd get my period like clockwork, I could almost tell at what time it would come, and then all of a sudden for a few months in a row, it would be all wonky, not come at the same time at all! Also, since you did miss that one pill, it might've just messed up your cycle a bit.
But I would take a test just to be sure--I'm sure the not knowing is driving you nuts!
Whiskers