What Treatment To Be Taken For Irregular Periods?

My age is 18 yrs , height-154.94cm, weight-50kg. I had suffered from irregular periods when it first started at the age of 9 years. After that i was prescribed to have martinor which had brought me regular cycles. But recently it has been found out that i have pcos and have been prescribed ovacet and diane 35(which i am having from the 1st day of my period , 1 tablet before going to bed at night). But i find myself suffering from severe stomach ache (lower abdomen pain) since the first day of my periods even in the 2nd day which was not there before. I usede to suffer from stomach ache a bit only on the first, it was not continuous. Am I being treated medically correctly?