I have to use computers for 9+ hours per day (no suggestions about 'use your computer less!' please).

I get various kinds of RSI: a little soreness in the hands and wrists, but that's not a big deal compared my main problem:

Pain in the sides of my body, under my arms and down the sides of my torso.

Driving worsens it. Exercise doesn't seem to help (maybe I need a special exercise). It could be posture related, but I haven't found a way to fix that.

Has anyone else experienced this? I find lots of people complaining about more typical kinds of RSI, but not like mine.

I am hoping someone with experience can recommend an exercise, treatment, or adjustment in how I use my computer.