Okay, here's the deal...you *have* to be gentle with yourself. You cannot second guess what happened...you just can't!
Maybe the epidural allowed your muscles to relax enough to allow powerful enough contractions to move him the rest of the way down and out?
Maybe the relief of knowing the epidural was coming allowed your mind to let go of any emotional reason for not dilating?
Maybe you were so exhausted from labor that the hospital really was the safest place for you...