Plan B should be taken within 5 days (120 hours) of unprotected sex and can reduce the risk of pregnancy up to 89%. But it is more effective the sooner you take it.
I wouldnt stress over it, wait for your period.

i had the same situation. i had unprotected sex on the 14th day of me ovulaying. i took plan b within 48 hours and i still have yet to get my period which would have been due on march 1. i just feel sluggish now.

Plan B has been known to mess up your periods, by making them come earlier or later.