This is a video of me back squatting (low bar) 1xBW 75kg, or 165 pounds. Pretty heavy.

Recently my lower back started to ache a little, so that got me investigating and stuff.

During my investigations, I took a video, and I realized that my back squat form is a little crooked. (I thought it was perfect).

Looks to me like my back is too arched.

I know I've been asking you guys a lot of questions, but since I have no coach and am a noob, I figured I'd milk you guys (metaphorically) for all the knowledge you have until I am a noob no longer (will probably take a while).

Come on, help me out. How can I fix this? And are there any other problems with my form?