From personal experience (and what I've read), Plan B can make your period a little wonky. Most likely what you are experiencing was a period, you may or may not get a "heavier" one in a week or so.
Implantation bleeding is VERY scanty. It would be light pink or brownish discharge.
If it's been 14 days after your pregnancy risk, you can take a test!
Thank you..I just took a home pregnancy test and it turned out to be negative.