Pressure in back, bottom left leg while squatting.

Started squatting a few months ago, I had to start at the bar. I've had a few problems along the way but things are starting to get pretty heavy for me. (PR 165x5) Right now, I have a problem with a pressure/strained like feeling at the bottom of my left leg, looking at a musculature diagram, I would say it is the tibialis anterior. Anybody know what form issue might be causing this? My legs position is the same on both sides, so I'm not sure why this is occurring only one side.

Not sure what other information to give. I could post a form check video the next time I squat. But right now I want to stop going heavy until I figure this out, because I don't want to injure myself.