Did you ever visit a chiropractor to diagnose this? which is the first thing I would have done if the normal sunnah treatments didn't work especially cupping, black seed oil rub and ruling out any new changes I have introduced.
You haven't given me much details, did this begin as a result of an injury you sustained before? or did this happen all of a sudden?
I suspect because the quacks spoke about pillows it's something you experience during/after or is made worse by sleep pointing to pinched nerve/rotator cuff rather then an issue with your joints. Did you change your mattress? bed? pillow etc prior this?
I foolishly one-time bought one of those hard "memory foam" mattresses I spent a lot of money on after decades of sleeping on very old cheap soft mattresses my body was used to, suddenly after a few weeks I began to slowly loose feelings in both my hand (everything below the elbows) this was happening very slowly (hence couldn't make the connection at first)
I was unable to even type on a keyboard, the description pointed to a possible damage to the ulnar nerve, I suspected the mattress and slept on the couch, each day I was getting slowly better and my strength in the arm returned. (had I not acted this quick, this damage would have been worse and taken many months to fix using therapy)
This is a very common problem people suffer from (shoulder, neck, elbows) with certain types of mattresses/pillow or beds that were newly introduced.
Is it just one shoulder? what's your sleeping position? what type of mattresses you sleep on? this sounds like a rotator cuff injury or pinched nerve from the little details you provided sxb