I know how tough this is... I have been there.

Have you tried ice in your lumbar and sacral areas? If the pain is generating there, you might see some relief.

There is a condition, which many doctors still don't understand, called RSD... and ice actually makes this worse. Do you have any swelling or discoloring of the skin? That would suggest RSD.

I use ice quite a bit, on my back and neck areas when I have arthritis flares.

If you get some relief with an ice pack (I use 3M gel packs that I got from Amazon), then I would try Lidoderms across the lower back. These numb inflamed nerves quite well. (however your insurance may not pay for these)

If you do get some relief from cold then RSD is not likely.

Your pain does not move? Increase or spread to other body areas? I'd use very lukewarm water and not hot water in that shower. Have you skipped the shower and compared that day to one that you did shower? That may show if something about the shower is a trigger. You could do that on a day you don't have to work, etc.

But as others here have mentioned, there comes a time when pain management has to be done and discussed with your doctor.