I'm getting a pain in my left hip flexor whilst squatting. I feel it whilst I'm warming up and I do my best to stretch it, then when I get to my working sets I generally don't notice it. Any ideas what I'm doing wrong? I've altered my stance a few ways to see if it makes a difference, it doesn't

(I have had a bad right lower back injury the last 9 months or so, could it be linked? I'm beginning to think maybe I'm putting a slight rotation or something in my lift subconsciously in order to protect my right lower back and thus affecting my left hip flexors?)