Prolonged Menstrual Flow on Skyla?

I would greatly appreciate some input here; I had the Skyla IUD inserted about a month ago. For the most part, everything has been fine. The first few days with it were quite painful with cramping and such, but that cleared up as expected. What concerns me now is that my period came on time, approximately three weeks ago. The problem is, I am STILL experiencing considerable amounts of spotting, nearly qualifying as a flow. I'm worried that such a prolonged period may be abnormal. Please help!