How Long Does Norethisterone Take To Start The Menstrual Cycle?

Hello .I was diagnosed with pcos 4 yrs ago.but now I need babies badly. My gyn put me on 5mg of norethisterone 3times daily for 7 days. Today is the 3rd day after the last tablet and still haven t seen a bleed. How long should I wait before I infor my gym abt this.thanks a lot