First postpartum period question.

Hi!

I had my c-section 8 weeks ago. I stopped bleeding fully at about 5 weeks and at my 6 week check up my doctor said my uterus was back to normal. And this Monday I started back at my bootcamp classes.
Since Tuesday I have had some super light bleeding, only wearing a panty liner, definitely not enough for a tampon (and it's dark red/brownish). I am exclusively breast feeding but I got my period early with DS1(I forget what is what like though) , and DS2 is now sleeping 7 hours between feedings at night so I am expecting it to return soon lol
My question is: could this be my body having my first postpartum period? Or could it be just some bleeding from starting strenuous exercising?
It's sooo light, it makes me think it can't be a period, but if my doctor said my uterus and everything was back to normal 2 weeks ago I didn't think exercise would cause bleeding/spotting!