Brown discharge, sorry!

Lucy
Hey ladies, 
I'm looking for some advice.  
I came off the pill about three/four months ago and so far my periods appear to have gone back to normal surprisingly quickly. 
My period was due on 4th November and now it's almost 7th November and my period hasn't arrived.  I have noticed a tiny little bit of brown discharge though since the 4th but only such a little amount that you can only see it when I wipe, (sorry!)...
I took a pregnancy test yesterday (5th) but it came back negative 😒
Does anyone have any suggestions as to what it could be? No doubt I'll go to bed and wake up in the morning and I'll have my full blown period. 
Any suggestions will be greatly appreciated!
Thanks xx