I always always without fail out on a posture corrector, or put on my lower back brace as all flares I have are lower back, I got one on Amazon I’ll share the link below. But I do that or apply a heating pad and stretch as much as I can, cause if you stop it before it happens it’s honestly not as bad! And saves you a bunch of pain for a week or so.
Back Support Lower Back Brace provides Back Pain Relief - Breathable Lumbar Support Belt for Men and Women Keeps Your Spine Straight and Safe - Medium Size 32''- 37" at Navel Level https://www.amazon.ca/dp/B01GS08CM8/ref=cm_sw_r_cp_api_i_JFRHJM0PVCCGKYRTJBZY?_encoding=UTF8&psc=1
I have those same problems, I mitigate them with a lot of things, but just like you It is really difficult to shower, I can't shower without my bell vacuum on.
^ this helps a lot when I'm not wearing my bell vacuum. I have no idea why, but it stops the pains. and discomfort, which sound just like this btw if you have time for a video:
https://www.youtube.com/watch?v=Mctx-FkdQ-c&t=4s
I got my bell vacuum from https://vacuum-bell.net/Small-Vacuum-Bell-for-Woman
I have to wear mine all day, but I feel fine when it's on.
I hope you watch that video. Explains the pains and symptoms that occur when your bones are pressing up against your arteries.
I sleep on a very firm mattress, sometimes the floor with some blankets or a mat that I have, this helps me a lot as well.
I need to get a new chair, I keep leaning to one side with this chair and there's this part of it that digs into my side and it sucks...
https://www.amazon.com/gp/product/B01GS08CM8/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1
Sometimes I wear this, it actually helps a lot to relief the chest pain / chest discomfort, i think it squeezes my stomach and my internal organs upwards so that my heart is not drooping so low inbetween my sturnum and spine... lol idk but it helps a lot.
Thought I'd mention it, I use it to try to reduce the swelling that the Vacuum bell causes, since I was wearing the vacuum bell 24/7