Hi,
Welcome to ehealthforum,
Brown or dark discharge can be due to prolonged hormonal birth control use, vaginal infections, ovarian cysts etc. Do not ignore your symptoms (especially since it has been persistent). Visit your gynecologist/obstetrician at the earliest for further evaluation and management. If you are sexually active (and if infective cause is detected), get your partner also treated simultaneously to prevent chances of re-infection and avoid having unprotected intercourse while both of you are on treatment course. Take adequate rest. Drink plenty of water. Maintain healthy diet.
Take care.