What Causes Delayed Period After Stopping Duphaston?

hi, i am 30 years old. I have consulted a gyne last month to inquire about my menstruation which appears to be less than the usual. i was prescribed to take duphaston. but i got scared of what could be its adverse effect so i stopped taking. now, my period is delayed for more than a week and i'm getting worried. is it a serious matter? pls. help. thank you.