From what I know it can mean numerous things. Sometimes your body wants to get rid of the old blood to get ready for the new. Sometimes it can be discharge from bacterial infections untreated. Sometimes it's a sign of a miscarriage. I will call your doc immediately and report it anyway.

I agree I would call the dr as soon as you can..

From my experience it only means the old blood is coming out. With pregnancy they say that red bleeding is bad.