to elaborate on the casting Billchao referred to, your first move on your downswing is over the top which gets you going outside to in- with a slice resulting from swinging across the ball. Correcting your plane will likely have you feel like your hands are dropping or re-routing to the inside on the downswing (but this will likely just mean less of an over the top move).
If look at your head, it actually move forward at the beginning of your take-away then sways back. Not sure what you have been trying to work on, but if it is a steady head, it may be that at the beginning of your back swing you are trying not to move it back off the ball (and are actually over doing it in the other direction), then losing control of it and swaying back. As BC said, keeping the hips more centered on the way back and then driving them forward may help to reduce the over the top move and keep you on plane.