there is a wonderful product called 'warmties' they have a website with a dot com dot au at the end

It's a wheatbag (or rice??) that you heat up and you can tie onto you with a soft cotton cloth. They are amazing for achy backs because you don't have to hold them in place!

Good luck!
Similar to warmties, there are band aid like heat packs that last 8 hours. Elastoplast and Nurofen make them. Works a treat.
Also, hydrotherapy has worked well for me.
Back pain is the pits.
Hope you feel better soon