Have you tried stretching that focuses on your back?
Then you progress to "tai chi" for beginners.
It helps your balance slowly and improve your breathing which distresses you.
Once you feel comfortable you can move on to moderate.
After that is start with yoga for beginners whilst continuing the tai chi. You'll be surprised gow much it improves your back.
It may help if you check your bed and matress that supports your back properly.
Get well soon and let us know how you get on ☺️🫂🙏