How do i know if a plan b worked?

Trigger warning / sexual assault

my now ex boyfriend assaulted me friday night while i was unconscious, i only got him to confess when i pressed him about bruises on me. i am not on birth control right now, but i did take a plan b yesterday. i haven’t noticed anything and im too anxious to wait to see if my period comes. will i know if it worked in the next few days or do i just have to wait it out?