When Does Periods Start After Taking Duphaston?

hi my wedding is next month and for the first time i have a delay in my period the doctor prescribed duphaston for one tablet a day only its my 3 day and my period didnt come yet is it normal should it come soon i am so afraid that i ll be period at my wedding i dont know what to do i am so stressed up plz give me an advise how does this medicine

work