Your knees are going too far forward, which is helping the bar to drift forward and you are lifting your chest. Sit back and hold your knees back. You won't squat with a vertical shin, but you have too much knee travel now. Had you filmed this from the rear oblique, as specfied in the sticky, I would be able to say if your knees aren't going out enough. Alas, I am not sure. Read the sticky, friends. I think one out of every three questions I answer involves me repeating that. Keep your chin down as you drive up with your hips. I would like to see you in some proper weightlifting shoes. Lastly, check out the bar position video. I would bet that all of this requires 15 or 20 pounds to come off the bar.