I sit long hours with poor posture and Im fine.
Years ago when I was 18 – 21 I used to get bouts of Sciatica, also had it for a few weeks this year after birth of newborn twin girls (constant bending over).
For me swimming was the cure. When younger I used to go once a week or more, just for a few weeks till it cleared up.
This year, I had quite bad nerve pain in back and hip, one session of light swimming in fun pool with family and I was on the mend and in few days it had cleared up.
Just try relaxing swimming.