It doesn't necessarily mean you are pregnant. Plan-B caused you to have your period early, so you really should count from when you had that period.

Thanks for the advise! Any more info, please let me know.

I agree with Eiri. I've had to take Plan B once before, and I got my period a few days after taking it. I think its because there are such strong hormones in it, and once they are done going through your system you can get withdrawl bleeding just like you do from birth control pills. I wouldn't worry about your period being late. It is probably that way since you bled just a few weeks before. However, you never know, so just incase I would take a pregnancy test to ease your mind. If you are 3 days late already then a test would be very accurate by now.