What Causes Irregular Periods While On Medication For Polycystic Ovaries?

I was diagnosed of bilateral polycystic ovaries before 8 months. since then taking treatment. contraceptive pills for 3 months and went on progestrone tablets from 16th day of menstrual cycle for 2 months. next 2 months, I dint take any hormone tablets. taking 1 glycomet 500mg tablet for 6 months at noon. The periods will come some days late everytime. Please explain the situation. What are the changes should I make to my lifestyle.