HI M 21 Year Old, On 19Dec I Had Sex

HI m 21 year old, on 19Dec I had sex with my bf n took unwanted 72 within 3 hours but I hvnt got any bleeding even after 4-5 days of taking unwanted 72 . I was expecting my periods on 28 Dec but missed thm n I had a home pregnancy test which was negative bt till now I hvnt got my periods bt I observed sm Brown discharge is that normal? Or is there anything to worry about? Pls help me