Took plan b and am on birth control what is the effectiveness that it worked? and am i pregnant took a digital pregnancy test and it was negative two of them?

Plan B ?'s: "Plan B" pills are essentially bcp's, but do not guarantee "100%" pregnancy protection. If your home pregnancy tests were done at the time your period was due, and were negative, they may not be accurate. Wait another week and obtain a serum HCG test to be certain about pregnancy, which is accurate even with low levels of pregnancy hormone.