Can't win for losing

So, recently (4 months ago) I had some blood work done just because my gut told me that I can't have kids. Turns out I have polycystic ovarian disease. Said that my cycle is off and my hormones are unbalanced so I'm not ovulating. Evidently my cycle was wayyyy over 28 days. So I started birth control immediately to try to regulate myself and get my hormones in check. However, since then I now have a 7-9 period every 14 days... why?!