Could Periods Be Postponed After Spotting Start?

hi doc actually my periods are due on sunday or monday since i've 2 attend a 3 day function starting from friday -sunday i thght of taking the norethesterone tab from tom onwards but unfortunately i saw some watery brown liquid discharge in the tissue so i started taking the tab in the eve immediately so will it stop my periods b4 friday? i usually have spotting for abt 2-3 days b4 my periods