Plan B Emergency Contraceptive

I made the worst mistake of my life last night. My friends convinced me to drink and I got really drunk. I ended up sleeping with this guy and we didn't use a condom. I am not on birth control and I took Plan B within the hour of having unprotected sex because I was terrified. Has anybody ever taken the pill? How effect is it? Side effects, any advice?

I would sincerely appreciate the support and advice because I am scared right now.