Hi Doctor,it's Alredy 1 Month, 2 Weeks Didn't Had Period,

Hi Doctor,it's alredy 1 month, 2 weeks didn't had period, so consulted doctor and doctor had suggested me to take the tablet Egest 200 i.e Progestrone Soft Gelatin tablet, for 5 days morning and evening by mouth. and alss she advised if period happens then to go and meet her on 2nd day of the period, if not then after completing the tablet, she advised me to do UPT test..Actually sine 2 years I'm taking treatment for irregular periods.My question is how this tablets helps and what are the precaution I need to take while taking this tablet? Please advise