Confusion with brown spotting

Been having brown spotting since last tues..spotting got really dark.and a little more in quanity than before for a few days but still only needed a panty liner and now ts fading out agajn..my period is supposed to come tomorrow (week after initial spotting) took a test sun. And was BFN..am i out¿This spotting is unusual I usually only bleed around the same time and it's very heavy and red