I´m dealing with an old low back injury that I thought that was healed

a bad rep two weeks ago (stiff legged deads) made it come back, but now I have an additional problem: a bunch of hours of unavoidable office work, seated position (the worse one in my experience for my low back pain).
I´ve been avoiding squats, deads, free rows, standing overhead presses and that stuff, but this is not getting better, because beaing seated makes it worse and worse. I try to stand up every few minutes and take a walk, and do slight stretching.
Pain is in the low back, right side, coming a little down on the leg. It hurts with every hip extension movement, being obviously any form of deadlift the worse thing for me to do. Moving, walking o even training upper body the pain disappears; being seated for a long time makes it worse.
Any ideas?
Thanks guys
