The brownish discharge following delivery usually doesn't extend beyond 3 weeks. You should have got yourself checked for that.
As you are not breastfeeding
it is quite possible to restart your menstrual cycles earlier than other moms.
The bleeding you had would most probable be a menstrual bleeding.
I'd advise you get yourself examined if the bleeding or discharge persists.
It is prudent to use protection while having sex now to prevent early consumption after a delivery.