What Causes Delayed Period Even After Taking Duphaston?

hi, i never had any problem during my periods just that they were irregular once or twice in 6 months.my doctor advised me to hae duphaston tabs for 10 days 10mg twice a day.which i took timely as she told me else i will start bleeding.its been 5 days since i got over with it but no periods yet.i had my last periods on 15th april. Thanking You