Hi guys, so I've been doing squats for most of this year without any problems whatsoever, got up to 120kg. Went OS on vacation a couple months back, dropped it back to 90 when I started again after 3 weeks off. I decided to start doing AtG squats, since I had always just done the traditional squat before.
I've noticed my last few sessions since I've upped the weight to 100-105kg that I'm feeling alot of pressure right at the base of my spine. This isn't while I'm doing the squat, its immediately after I get the bar back on the rack and stand up straight. Right now it's not feeling too good and I'm wondering if I should just go back to regular squatting. Any advice?

Do you have the range of motion in your hips to do ATG squats without rounding your lower back? I'm not necessarily pointing the finger at muscular inflexibility, either - sometimes it's just a matter of geometry.