Crazy periods

So after the birth of my daughter my doctor had me start birth control. It was easy going took the pills on time. I had the usual PMS. After the first month I noticed I started having a period every two weeks. This lasted 6 months. Now almost a year on it and my period seemed to taper off from 5 day light to 4 days to this month nothing. Should I be concerned. Or wait 2 weeks and test? Hmmm...Idk.