Hi, My Period Is Usually Very Regular Every 28 Days.

Hi, My period is usually very regular every 28 Days. However last month it was delayed for 20 days so the doctor prescribe pimolut for me. I have taken 2 tablets a day for 4 days and one tablet for one da. its now 4 days since I stopped and no period yet. My question is how long it should take after stopping it? does it have any side effects?