What Causes Delayed Periods With Brownish Black Bleeding?

hello,i was expectn my period on january 8,but it didnt show up,then on 11 january ,i had this bleeding which was very dark brown at the beginning and became black towards the ending,it lasted for 5day,now my qestion is what do i call this,a late period,implantation bleeding,decidual bleeding or miscarriage,i dont understand,its making it difficult for me to know when next to expect my period,dnt knw when to actually start counting and am having pregnancy signs