Your story reminds me of a philosophy professor in college who wrote on the chalkboard: "God is dead--Nietzche" followed by "Nietzche is dead--God." Your certainty is not unique. You may want to read Sebastian Junger's recent book "In My Time of Dying." He was an atheist with certainty that an afterlife did not exist until he nearly died due to an abdominal hemmorhage. What he experienced caused him to question his "opinions" about death and the afterlife. Be careful about stubborn certainties. Sometimes life brings you experience to teach you lessons in a difficult way.