Why is there a brown black heavy discharge from my vagina? Had it for over a month, and on implanon. Is it bad and how do I stop it?

Bleeding. Brown color comes from slight blood mixed discharge for how long you have implanon it could be effect of Implanon also a lesion in vagina, cervix , infection fibroid uteus can cause it get a complete gyn exam wait for effect of im[anon to go away if you have just inseted implanon. It may go away if not get vaginitis cervicitis treated last treatment will be to remove implsnon.