I’m pretty on top of things when it comes to hip mobility but a few weeks ago I squatted and the next day my hips and low back were super achy. It was hard for me to go into any type of back flexion while doing everyday activities… It started feeling better so the next week I was starting my warm up sets with back squats and when I did a set of 295 on my fourth rep my lumbar spine felt like it was getting smashed together. This is not considered heavy weight for me ( my max is 450). I try to make an effort to brace my core and open my hips while squatting, pretty much all of the normal stuff when it comes to good technique for squatting. I will say that I had an appendix surgery a few months ago and had lifted heavy a few weeks later without any pain. This pain was about a month post op so it’s not like It was my first time back lifting heavy. I stretch hip flexors and piriformis pretty frequently as well. Any advice would be greatly appreciated.