Implantation bleeding 2 days after missed period.

Hi all, 
​I was due to have my AF on 10/01/14 and On  10/03/14 at night started getting really bad cramps, I thought AF was going to start, but when I woke up there was not the usual amount of blood and after an hour it was only a little of brown and for the rest of the day it was all the same, I didn't even had to change my panty liner, and the second day it was only when I wiped and its still going on, I've been having cramps headache and getting very dizzy lately. Any advise? I also had a test and it was bfn