Hello, Dark brown discharge on last 3 days of active pills may be associated with implantation bleeding in case of failure of the pill or old endometrial tissue combined with vaginal infection. Hormonal imbalance and stress/ depression are other factors for causing the same. One blood test for beta-HCG & vaginal swab test are required to confirm the diagnosis in collaboration with complete hormonal assay (if there is persistent discharge). Consult with your gynecologist for suggestive measures. Avoid stress by regular deep breathing/ yoga, take healthy diet with Vitamin & iron supplements, control body wt, maintain genital hygiene and take a sound sleep. Be well & take care.