It may sound funny but I found these guys on you tube.
Absolute Best Exercise for Sciatica & Herniated Disc- McKenzie Approach. - YouTube
I had sciatica really bad and these guys really helped. When I do get the pain now it's very minor. When it used to get really bad I saw somewhere that you should sit on a tennis ball. You need to work the ball to find the right spot. That really worked well when driving. I feel your pain!
Steve