sometimes mild to minimal bleeding can cause brown discharge due to degardation of blood.
hoever if you are having prlonged and massive brown discharge it needs to be evaluated by a doctor.
i would advise you to take a pregnancy
test in another week if you dont have your periods.
have healthy food in the mean time, pleanty of water and avoid stress
sometimes during very early part of pregnancy the test may show negative results.
if the symptoms worsen call your emergency number,
please use condoms the next time.
i hope i have answered your query.