My Gf Last Periods Was On July 7 After That

My gf last periods was on july 7 after that till aug 24 she was no.periods.. On aug 24 she was taking Norethisterone tablets for 5 days(2×5)..after stopping the tablets after 2 days she have a bleed for 2 days and the third day it wil be only spotting..her normal periods was 4_5days... She is having head ache also.. Is there any problem.. And when did she have the next period