I Had PCO And Got Pregnant With Help Of Medicines.After

I had PCO and got pregnant with help of medicines.After 4.5months of delivery I got my periods. After that no periods. Now it's been 9months after I delivered. Doctor prescribed susten300 and ask to take it for a week and wait for 10days.its been 11days now and no signs of periods.
And I don't think I'm pregnant(did home pregnancy test before I start taking system tablets) .What may the other reasons that I still didnt get my periods. Kindly update. And let me know whether it is possible to regularize my periods.