Suggest Treatment For Irregular Periods

I am 32 years old.from 2 mnths i had irregular periods ans on consulting doctor, she advise me to take sysron n lablets for 5 days. after stopping the tablets with in 5 days ii got may periods, but in this month i did not have period as my date of period already passed. I am very much worried. Plz help n tell me what can be the reason.