Implantation Bleeding

Christine
How long does implantation bleeding last?  About a week (maybe a week and a half ago) I had 1 tiny dot.  Then a few days later,  discharge with a bit of pink blood.  Last Sat I started having very light pink discharge that has since changed to brown.  I'm now 3 days late and have had 2 negative tests.  Does this sound like IB?