Thanks for the query. Contraceptive
pills can cause irregularity in menstrual cycles.
As you are taking duphaston
that can also be a cause for delayed periods.
After stopping the duphaston, in one week you can get withdrawal bleeding.
Usually either contraceptive pills or duphaston can be used to regularize the cycles, no need to use both unless there is specific indication.
So you discuss these possibilities with your doctor and proceed accordingly.