Quoting Julian's Momma :" Sometimes I get it too, but like I said, not this much or for this long. Oh well, I'll find out soon lol. "
good luck... IB can be brown too.
also idk your cycles have been normal but i know with me i always had brown spotting in the middle of my cycle this time,,, it was werid. maybe its something similar..
hope you get the answer you want