I’ve started having issues recently, too. After a work injury, I finally saw my GP, who recommended Physical Therapy, which has basically just been a guided workout with some yoga moves worked in over the course of an hour.
It hasn’t fixed my pain yet, but it’s made it better, and my pain was explained in a way that makes sense (my shoulders and core weren’t as strong as they should have been, placing undue burden on some of my backmuscles).
If you don’t want to go to PT, I’d strongly recommend just slowly doing 10-15 minutes of simple stretching like what you might have done in Gym as a kid. Stretch to the point of mild discomfort, not pain, doing each stretch 3 tines for 10 seconds. It might be worth looking into some basic yoga poses that target your particular pains (or the ones that you want to target first).
I’ll bet you’ll notice good results after a week. If not, definitely go see your GP again.