How Safe Is Taking Cycloreg For Delay In Periods?

Hi! I have been asked to have cycloreg twice a day for 3 days since i have irregular periods and this time it has been delayed more than usual. My doc said I might get my period 5-10 days after I stop the medicine and not before that. What is the reason for that delay? Also, if it still does not come, is there any other medicine I can safely have?