Why am i having very similar symptoms of early pregnancy but i took a plan b and i tested negative on my pregnancy test.also why am i bleeding 6 days after taking plan b?

It is common for Plan B to cause bleeding a few days after taking it. Early pregnancy symptoms are nonspecific and not at all diagnostic. Your pregnancy risk is probably low at this time but more information about your cycle and timing of the Plan B would allow better evaluation. You should probably repeat the pregnancy test in a week or two as a precaution.