I'm going to have a completely different tack from everyone and say you sound like your overtraining your lower back.
You do 3x5 squats and deadlifts every session, which you work to a PR. Along with that you might have 6 or so other exercises that are going to smash your back depending on what you do (eg stiff legs, bent rows, hack squats etc etc). Thats all fine at beginners weights, but you're not lifting beginners weights anymore and it sounds like you're getting smashed.
I think you either need to periodise or rotate exercises more often like westside/doggcrapp do. Most pros use models like PPP or 5/3/1 where they work to a max over a period of weeks which makes recovery a hell of a lot more easier. Conversely some pros max out every session, but most of them use singles (which are going to accumulate far less fatigue than 3x5) and rotate exercises weekly to prevent getting fried as opposed to running one lift week in week out.
Id pick one of those methods.
You are fairly close to the money.
My training is quite basic.
Legs/shoulders for example-
Squats
50% effort x 9
75% effort x 7
Max effort x 5 x 3
Hamstring curl, calf raises, seated DB shoulder press and BB shrugs, all the same rep range, that's in, in and out in 45 mins.
For Back it's Weighted chins, deads, T-Bar rows, lat pulldown and curls, again all done in 45 mins.
I have found it's got worse the less I do, not sure what I should change because I am only really doing 1 major lift that smashes the lower back per workout, not sure how I could do any less?