What Causes Brown Discharge,pain In Pelvis And Frequent Urination?

Hi, I've been having brown discharge for about a week now. I usually start my period off about an hour before I get a heavy flow. I feel a dripped feeling on my left pelvic area and my kidneys ache. I took a pregnancy test and it was negative, although I've been urinating all day every so i not sure if i got it wet enough. Any thoughts on what it could be?