You aren't getting deep enough in your backswing.. a good indicator is your right elbow at your transition, whenever you look at tour player their right elbow is tucked very close to their right side at the top of the swing.
You look like you are also over swinging, I realize that you may get more power from a longer arc but whenever you reach that far in your backswing your hands have to slow down in order to let you shoulders catch up in your follow through resulting in a loss of momentum and power.
An in-to-out plane is a natural power producer and if you can start swinging that way you will feel an effortless power sensation that is truely awesome.
If you can get your hands deep at the top you will be at a more natural position to swing in-to-out.
Try taking the club to parallel with a chest turn then use your shoulders to get the club deeper.
Its tough and I'm working on the same thing right now... good luck