I take a drug called Naproxen 1000mg, it lasts all day long and is very strong. There are also other strong NSAIDS that you could try like
Diclofenac and Indocid etc.
You will need a Dr to write a script for those.
I'm not suggesting that you take these on my advice alone, but you might want to talk to your Dr about them.
There are also other types of drugs which may help you, such as anti-convulsants, which have pain killing properties as well.
And of course, keep up the gentle excercise.