I started doing legs pretty hardcore like 2 months ago and now I've been having some back pain which I can almost positively attribute to barbell squats. I am 6'2" about 200 lbs 14% bf fyi. I do my squats on the smith machine bc I do not have a spotter that I trust. I wonder if the pain is bc my posture may be restricted on the smith machine. The pain only comes after heavier sets( I'm worried about my knees so I max at 275lbs for 8 reps on my last set). Any advice or a different outlook on this is appreciated. Thanks in advance.