HI DOCTOR, I AM SUPPOSE TO HAVE MY PERIOD ON

HI DOCTOR, I AM SUPPOSE TO HAVE MY PERIOD ON THE 6TH OF NOV WHICH IS STILL IN TIME TO FINISH BEFORE MY HOLIDAY. HOWEVER MY PERIOD DID NOT CAME ON 6TH, THEREFORE I TOOK Norethisterone ON THE 7TH NIGHT.. HOWEVER TODAY (9TH) I REALISE THERE IS SOME SPOTTING (BROWN COLOUR) , DOES THIS MEANS THE Norethisterone DOES NOT WORK OR IT IS NORMAL AND IT WILL STOP MY PERIOD?