Might i be pregnant even if i took plan b?

Yes: The effectiveness of Plan B depends on when it was taken and the stage of your cycle. Sometimes pregnancy tests are negative if taken to early. See if you start your period and then take one more test after that to be sure.

Yes - it is not: 100% effective. Plan B One-Step is up to 89 % effective when taken within 72 hours (3 days) after unprotected sex. It can reduce chance of pregnancy by up to 95% if used within 24 hours. It continues to reduce the risk of pregnancy up to 120 hours (5 days) after unprotected sex, but is less effective as time passes.