Meant to say upper back looks like it isn't in extension on my first reply. Sorry for the confusion.
Are you certain the bar is in the right place and low enough? Check out Nick D's bar position video.
Where to Put the Bar for the Squat with Nick Delgadillo - YouTube
A couple of these are high, so please make sure you're posting sets to depth. Also, you're not driving your hips at all. You're lifting your chest and head as soon as you come out of the bottom.
Gonna have to sort out the upper back. Make sure the bar is in the right place, then lift your chest up and bring the elbows down. You'll have to practice holding that while getting leaned over at the hip to set the back angle. A cue I've stolen from another Nick D. is to think about rolling the bar down your back as you start. Don't actually do that though.
Do you live near a coach?