Had surgery on mine years ago. Can tell if I start to overdo things but find laying on my front gives relief by changing the shape of my back (especially adopting this when going to bed) Try all fours and gently flexing your back by arching up and then relaxing. Can someone give you back and shoulder massage?. All this not v helpful while at work I know. Obviously all the changes are taking their toll and mainly your back is complaining at being in the sit position too long. Just keep trying different things and I hope you find solution soon or you may be in for ongoing problems.