Mine is off center as well. I noticed it after I used one of those plastic cases (Seidio Innocase) for a while. After a few months I took it off and noticed that the top and bottom are a bit off. In fact, I posted a
similar thread a few weeks back. I never dropped my phone and it was always gently used. I guess it is just part of regular wear and tear... would love to get it aligned again though if possible.