If i have $0 fed withholding (on my check) Did i add too many exemptions?.and will i owe a lot by tax season?

I think I may have filled out my w-4 wrong. I'm single, Head of household...and somehow i put 3 exemptions..and when my check came, i noticed absolutely no money taken out Federally...can someone help me? ...I don't want to owe all of it in some huge sum.