When you say "unprotected sex", you are "unprotected" for spreading sexually transmitted diseases, but you are protected against pregnancy.
If you're on a birth control pill and taking it correctly, you don't have to use PlanB if you have sex. The pill will keep you from getting pregnant.
I know you hear cases where women get pregnant while taking the pill, but in clinical trials, where a nurse witnesses the woman take the pill at the same time every day, the women get pregnant at a very, very minimal rate. You're covered if you're on the pill and you're taking it correctly, statistically.
Did you just start taking it? When you're on the pill, you won't ovulate and so won't have an actual period. But when you're on the off week, you do have a little hormonal bleeding. It should be light. If it doesn't happen, you still just start with the next pack and all is well.
Are you still taking the pill or did you stop after you didn't start to bleed?