Very light period

Markie • 25, Engaged to my best friend! Been together since August,2014 got engaged February 19,2017. :) :)

I'm not sure if it's just me, but I'm having a very light period. Not enough to even fill a tampon, or a panty liner. Sorry for grossing anyone out by this, but when I wipe, it's pinkish red, been like this for a few days. I've taken 3 pregnancy test before I started seeing blood, and they came back negative. I've had this happen before but it's been years. Has anyone been through this? Can someone tell me what is going on?