Wat ben ik?

From the box (translated from Dutch):
I am a person but I don't know who. What must I ask before I know?
A bag? No. A hat? And do I have something in my hand?
Am I wearing something blue? Am I in the countryside?
Am I the pilot? The cook? No, I must be the fireman!
But I must be sure before I look.

Which question shall I ask to get the right clue. Hurray! I've found it. Everything points out that I must be the nurse!