Hello, thanks for using HCM.
Brownish vaginal discharges do not appear normal even if the amount is small. Abnormal vaginal discharges are associated with infections which could be sexually transmitted or not. Vaginal infections are a common problem regardless of sexual activity or not and are easily treated. However, sexual activity predisposes to STDs.
Its most likely you have an infection which could be due to sexual exposure from the unprotected intercourse
or not. What ever the case, you need to be seen by a physician for appropriate evaluation and tests including vaginal smear and chlamydia be done after which appropriate treatment will be given to you.
Best regards and hope this helps.