Brown discharge 3 weeks after period.

molly

hey ladies! i was experiencing some dark brown discharge three weeks after the first day of my last period. i assumed at the time that it was just the beginning of my period, but the brown discharge lasted 4 days and my period never came. I took a pregnancy test today (the 16th). and it was negative. if i am pregnant i feel like i gave myself enough time for it to show up on the test. could the discharge have been in place of my period? or is it an indication of something else.

regular period december 5-8, dark brown discharge dec 26-30, negative pregnancy test jan 16.