I also had implantation bleeding which was my first indication that I was pregnant. I didn't even get a positive until ten days after missing my period and that whole time I was using high tech pregnancy tests and using first morning urine. I say give it a lil more time! Don't give up hope just yet :)
wait another week and then test again
i will be going to the dr in another week if i still haven't gotten my period. but the spotting is still kinda odd
Go to your doc for a blood test?