Back pain from trying to correct posture
Before we get into anything, I know the obvious answer is physiotherapy. I'm extremely tired however and not in any actual condition to be going to physio until I've recovered somewhat, so it has to wait for now. Meanwhile,
my upper back muscles have deteriorated it feels like to nothing. Even washing my hands in the bathroom I need to slump down to lean my elbows down to the sink because the muscles in my upper middle back, around the lower shoulder blades in specific, are so weak I don't feel like I can hold up the weight of my chest and head with them. It's gotten worse and worse over the past few years - this is also the region I have the most instability and chronic pain in, and where I get a ton of pinched nerves, it's a constant problem in every way imaginable from the middle back up to the bottom of my skull.
I've been trying to take a few minutes here and there to practice sitting straight to train the muscles again, because that is the absolute most strain I can put on them, the absolute most weight I feel they're capable of handling - but as a result, even from this that feels like it shouldn't even be called "exercise" to me, my whole back all the way down to my hips stiffens, spasms, and develops this constant throbbing/burning fibromyalgic pain that radiates all the way around to my stomach and my shoulders hurt so much because the correct posture makes the trapeziuses relax and then they spasm up again.
Is there... something even gentler I can do to start with?