What Causes Delay In Period Even After Having Sysron N?

Hai . I have nt got my periods it has been around 15 days . Never experinced it before . Consulted doctor and she suggested to take sysron N for 3 days you will get your periods. It has been 5 days that i have stopped the tablet. But still i havent got my periods. Can you tell me after how many days i will get my periods or there is any problem