What Causes Heavy Brownish Discharge During Menstruation?

i have been on my period for 37 days straight now...i have had a few HUGE clots..and by huge i mean 2 in. wide and 3 in. long..the only time it was heavy was when i had the clots other than that it was fairly light. also its been mostly brown in color, unless i wipe then its red. whats wrong with me?