Squats 3x6 255lbs 18 years old

[Stress]

Hello,
I'm an 18 year old guy and I have been squatting since last year. After 2 months of squatting, I starting getting bad pains in my lower back until I couldn't even deadlift 135. I couldn't squat nor deadlift for about 6 months. Now I'm back at it again and I'm at the strongest I have ever been. I still think my form is a little off. Currently, I'm a full time university student and I can't afford a coach to teach me good technique. Here is some footage of me squatting 255. Any criticism or coaching cues will be greatly appreciated.

Height: 5'11
Weight: 209 lb
Thank you for your time.
YouTube

[Jason Cross]

Your depth is too low. Try to cut those reps off sooner. Watch this video where rip talks about not sacrificing lumbar extension to achieve depth. Back rounding at the bottom of the rep probably contributes to your pain.

[Justin Smale]

First off, you'll get much better feedback here if you look at the sticky at the top of the forum regarding the angles to record your videos. In these it's hard to see things like bar position on your back, elbow position, etc.

It seems like you are looking straight ahead (and I'm guessing there's a mirror in front of you) and you should be looking 4ish ft in front of you on the floor to hold your neck in neutral position and preserve the tightness in your upper back.

You're going down way too far, you don't need to go ass to grass, just go until your hip crease is below the top of your kneecap.

WHY ARE YOU DOING 6 REPS?

There seems to be strange hitch in your drive upwards. On your ascents it almost seems like you're thrusting your hips forward while you lift with your back. I'd also hazard a guess that about halfway up you start pushing these from your toes since your knees come forward as you're lifting your back. Your bar path looks like it's wandering a bit too, it doesn't appear to me that it's staying over your mid foot. I'm guessing these things are all connected. If you kept the bar over your mid foot, you wouldn't be rocking forward onto your toes and your knees wouldn't come forward on the ascent and it would be smoother motion. I'm not knowledgable enough on this, but to me this looks like it needs a few tweaks, see what other people say here.

I could be wrong but it also looks like your knees are leaking inwards on your ascent, but you need a new camera angle to confirm this. Shoot your next ones from the rear quarter like the sticky says. And stop doing 6 reps.