What are the reasons why my periods are brown in color and has clots ? take note i also have pcos and am sexually active.

True "PCOS" is usually without ovulation, which allows constant estrogen stimulation of the endometrial lining, which may break down on occasion, leading to clot formation and sometimes light bleeding. This is not actually a menstrual event, but represents bleeding from what is called "unopposed" estrogen, since ovulation is not an antecedent with PCOS.