Abnormal period!!

Judith

Hi guys..,, okey,, my period is late for 3 days and then I tried test and it was negative, following day I got one day period it was heavy and then stop and got a dark brown discharge for 3 days,,this is never happen to me before,,..what should I do??do I'm pregnant??is there's something wrong with?? PLEASE HELP ANYONE OUT THERE GIVE ME ADVICE, THANK YOU