Your body may be preparing to start your period. The brown discharge is called old blood. The first couple of times you may have this discharge but you will eventually have the red blood. I would not worry unless it has an unusual smell, last for over a week or if you start having bad pains before discharge. If that happens go get it checked, until then just relax and see what will happen. Best wishes.
Sissie
Your best bet would be to consult a gynecologist.