What to do? no period since Sept. 17, 2016. in pain below belly.

Question

Hi Doc,
A certain Doctor advise me to take medication (Duphaston)for 6 months starting March 2016-August 2016, since I have PCOS. Every month, 1 was taking a tablet good for 10 days  (every calendar day of 5th-14th), 1 tablet a day, so for 6 months of taking medicine, im having my period every 17th of the calendar day..Accordingly, ill be having my regular period after 6 months of taking duphaston.
But this month of September, i dont have period yet. I tried PT last September 18, 2016- it was negative.

For your advise pls.