as u said u should get ur period by 5th and its nearly 15 days now so i advise u to better take urine pregnancy
test first and exclude the pregnancy and then if its negative ,nothing to worry..
registrone is a hormone which helps in regularising the periods or even in delaying periods for some causes.
taking it for 3-5 days generally help in regularising the periods..but b free if ur preg test is negative and wait for some days for ur period to return..
there might b hormonal
disturbance which is leading to delayed period due to ur tensions and also due to i pill
u have taken..
so nothing to worry..just wait