Seriously.... how are you holding the bar on pressing movements, like bench? Do you have the bar rolled towards the knuckles are back towards the heel of your hand? Some people have had hand/wrist issues and by moving the bar towards the heel of the hand they can take off some strain and end the pain. By moving the bar towards the heel you don't get to wrap your thumb as easily, but on pressing movements I don't wrap my thumb anyway.

This may or may not have ANYTHING to do with your issue, but I thought it was worth typing in.