question: I noticed couple of blood drops 2 days ago in the morning (this was about 5 days earlier than my usual menstrual cycle).  I had unprotected sex with my husband that night assuming that it was safe.  Since then, I only noticed another couple of blood drops yesterday & today.  I am curious if I should take the Plan-B pill to prevent pregnancy (I could wait another 24 hours as the window to take the pill is 72 hours).