I was having constant soreness in the lower back for months when i was trying to touch my toes or if i was curving my back. Its was not hurting bad when i was doing deadlift or olympic lift but i was feeling very week when i was in the bottom squat position. I went see the physio after like 3 months and here was the diagnostics.
After a couple of test, the physio figured out that my spine was not bending at the good place. There is a muscle around the spine called multifidius. My multifidius was kind of sleeping and i was never using it. So, all my spine on the lombard curve ( bottom) was stuck like a rock.
I went for 2 times a weeks for 3 weeks getting small electric shock on my multifidius to tell my brain how to use it. There is a couple of exercices after that to make the lower spine move correctly and the pain cause away. I dont know if my post is relevant to you but i was pretty scared about my back and at the end it wasn't that bad.