Should i be worried?

Karizma
IM 6 and and half weeks PP. I started bleeding heavily about 2 days ago. Its like a period. The blood was dark the first day now its bright red. I had almost stopped bleeding completely then this just started up. Im having cramps too. It feels like a period. But my doctor told me i shouldnt be having a period because I'm breastfeeding. I did start working out a little early im not sure if that could be why or not. But im going to call my doctor when they open just to be safe. But has this happened to anyone else?