In this circumstances, you should undergo one blood test for beta HCG level and TVS scan to exclude product of conception or implantation
bleeding which is mostly associated with brown discharge.
In exclusion of pregnancy, other reasons are hormonal imbalance, vaginal infection
and may be co-existed with stress/ anxiety, thyroid disorder
, irregular diet habit etc.
Treatment depends on underlying etiology. Consult with your gynecologist at the earliest for other relevant investigation if any.
Avoid stress, take healthy diet with iron supplements
, control body wt, maintain genital hygiene properly and take proper sleep.
Be well & take care.