I Am Taking Regestrone Sandoz To Regulate My Periods (

I am taking regestrone sandoz to regulate my periods ( 1tablet for 3 days ) . I got periods on 5th day after completion of dose but felt the flow was lesser as compared to usual periods and it was brown discharge and kind of spotty .
I have done the pregnancy test it was negative .kindly suggest what should i do
Feeling nausea, fatigued and tired from few days