Its possible to still get pregnant even taking Plan B since its only 85% effective. I got pregnant off of Plan B. What you need to do is get on birth control and take it on a regular basis since Plan B isn't good to take all the time and taking it twice in one month is horrible for you. It is for emergency purposes only and can really mess up your body. Take a pregnancy test if negative get on birth control and if positive contact a doctor.
If you have health insurance, go to your doctor. A friend of mine took Plan B once, that I know of, but no bleeding. I THINK it can INDUCE your period though, but still go see a doc or go to a clinic. There is probablyh a 1-800# on the Plan B box/instructions, etc. try calling them :) good luck