Suggest Treatment For Prolonged Menstrual Period In Case Of PCOS

i went to a dr for a problem with not having my period and she diagnosed me with pcos...i was prescribed metformin and said that it should help regulate my periods..i started taking the metformin and i got my period in like 3 days of taking it...that was in nov and now i am having a problem with getting off my period...pls help!!