Why do i have brown spotting a week before my period?

Orchestral practice: The endometrium (lining of the womb) begins its' shedding process with the withdrawal of hormonal support which can cause premenstrual brown spotting of old blood. Just as a conductor has a dress rehearsal (practice) prior to the actual concert so too does Mother Nature do the same. The exception, is pre-menstrual staining(spotting) due to uterine fibroids which your GYN MD can assess.