I took primolut a day after my period started last month n i had unprotected sex. it didn't really stop my period n now period is late. y is that?

Primolut: "Primolut" is a synthetic progesterone and can be used for birth control, If the Primolut was discontinued, you could be pregnant, but if you continued the Primolut throughout the month, your period may be delayed. Progesterone containing birth control works by altering the lining of the womb to make implantation unlikely. See your healthcare provider and get a serum HCG pregnancy test to be sure.