Implantation bleeding??

Becca
Hi
So I was 3 days late on what I thought was my period, my cycle is usually 26 days, I thought I came on on what would have been cd 29 however I have had only 1 day worth of bleeding, none through the night and nothing today at all for the past 5 hours (this would usually be day 2 of my period and would be heavy) however the blood is red and from what I have read about implantation, it should be brown / pink? 
Also when people say dpo, are they going off the latest day on glow of their ovulation period or the 1 day they were most fertile? If it's the latest day of their fertile period then this bleeding started 12 dpo if not then it was 19 which I believe to be too late?
I hope someone can shed some light on this situation for me, I done a pregnancy test on cd 26 which came back negative. I haven't had any usual period cramps only what felt like a bruise near my left hip. 
Thanks in advance :)