F.E.A.R. 3 man mode achievement plz help?10POINTS?

I recently postd a question on how to beat the last mission of fear 3 on insane dat no one answered.so i beaat it on my own.and i didnt get the achievement.i dont kno y.i beat the whole thing on insane.heres what i did.i chose replay mission.chose paxton fettel.and played as him on missions1-4.i chose point man on mission 5 and beat the game as him.i kept the difficulty on insane.yet i dont have the achievement.so can anyone plz tell me what i might have did wrong.10Points best answer.