What Causes Delay In Period After Taking Primolut N?

Hi My OB gyne advised me to take Primolut N for 5 days (3x daily) 10 mg because I am not having my period for more than 3 months. But after taking the medicine for the prescribed period of 5 days, it has been 4 days now and im still not having the menstruation.How long should I still have to wait?