What Causes Lower Back Pain And Light Periods?

I have been on NuvaRing for about a year and a half. I am suppose to remove it on Sunday, April 11. I usually start my period on the Wednesday or Thursday after I take it out. I started my period today, at least I think so. It is very light but my lower back is hurting and I had some lower abdomen discomfort (cramps?). This has never happened and I am concerned.