I spotted after taking Plan B. If you read the box it says you can take it within 48 hours and it will be effective. I am also pretty sure that implantation bleeding is more than just a little bit of pink once.
@Baby k yea my period is due in 6 days
No spotting isn't common the more time you take to get a plan b the less effective it is. You might have waited too long and got, got are you close to your period ?