What Causes No Period After Stopping Duphaston?

hi doc. my last day period is on 7th March, and i was prescribed with 10mg duphaston twice a day for 5 days. it is now more than 7 days from the day i stop duphaston, but no period yet. i don't have any sign of period, but my breast is really sensitive. Is there any chance that i might be pregnant? my UPT is negative a week prior.