Yes, you could be pregnant. If you think you were ovulating between 6-11 of February and you took Plan B on February 6, it won't do a thing to prevent pregnancy. Plan B delays the onset of ovulation. If ovulation has already begun, Plan B won't stop it - it's too late then. You might or you might not get pregnant.
If you KNEW you were going to be ovulating between 6-11 of February, then WHY did you have unprotected sex on February 5? Sperm cells can remain alive and capable of causing pregnancy for several days afterward, if you begin ovulating during that time.
It's possible that the light pink spotting you saw was "implantation bleeding", which happens about 10 days after fertilization. If that's what it was, that means for sure that you got pregnant.
Ordinarily, I would tell you to take a pregnancy test if your period is at least a week overdue. But, because you took Plan B, who knows WHEN your next period is going to be? Plan B messes up your menstrual cycle big time. You might have an early period this month, or you might not have one at all. You might not have one next month either. That's a side effect of Plan B.