What Causes Prolonged Vaginal Spotting?

hi i would like to know what possibly could cause me to be spotting for more than twoweeks almost as i was diagnosed with pcos,marfans syndrome at the time endo was ruled out but the colours of the spotting/discharge varies and im having a bit of a flatulence dilema. its highly unlikely that pregnancy could be a factor.since i dont ovulate and i weigh 55kgs and my height is 188cm..could it be something more drastic?