First Period? TMI

Olivia • 22 years old, single momma 👣 Dominic A. was born April 28, 2016 👶🏼
I'm currently 6 weeks PP and I have not been EBF. My husband and I had sex a few days before the 6 week mark (I couldn't wait LOL), and the next morning I had dark brown bleeding with cramps. The Dark brown blood turned into red, and became heavy and so did the cramps. It felt like what my periods used to feel like. However, this morning the bleeding has stopped all together and the cramps are completely gone. Before, I would have my period for 6-8 days with a 28 day cycle. I feel like that wasn't my period, but maybe I'm wrong?