What Causes Menstruation Along With Abdominal Cramps While On Nuvaring?

I was on NuvaRing for 2 months. My gyno told me I could skip my periods by wearing it for the full 4 weeks and immediately replacing it with a new one. I did that and with in 2 weeks, I started my period with my NuvaRing still in. I still have my period 2 weeks later. Its very heavy with cramping. 4 days ago it was time for my NuvaRing to come out, I took it out and continued my birth control with pills instead of the ring. My period has not stopped or let up. Is this normal at all?