Hi,
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The brown discharge that you describe could suggest possibility of vaginal infection, breakthrough bleeding, hormonal changes due to stress of infection/medication use, thyroid abnormality, endometrial changes etc. Go ahead with your appointment and evaluation as scheduled. The examination and evaluation done will help to identify the underlying cause. Treatment as appropriate (based on examination findings and investigations results) would be started to help you. Avoid vaginal douching, or use of harsh soap or perfumes in the area. Use loose cotton undergarments and avoid use of tight fitting clothes. Be in regular monitoring and follow-up with your treating doctor/gynecologist and report any new/abnormal symptoms immediately. Drink plenty of water. Take adequate rest. Maintain healthy diet and lifestyle. If infective cause is detected, and if you are sexually active, get your partner also treated simultaneously to prevent chances of re-infection, and avoid having intercourse while being on treatment.
Take care.