Brown discharge on period week

Janny
So ! I am freaking out right now . I'm on birth control and been on it for like 3 years . This month I'm suppose to start my period on Tuesday but nothing . On Wednesday I have a little blood ( sorry tmi) than rest of the day it's just brown spotting and than that's it . Today pretty much nothing and some brown discharge here and there . I took pregnancy test and its negative . Anyone help ?