I also have sciatica and this sounds like it. Be careful if you're shifting and try not to favor sides. I shifted a lot and ended up with bursitis in my right hip. Try one of those donut seats, they aren't comfy but help take pressure off. You should try a gel cushion for your chair, they are pricey but if you have an occupational therapist (or physical) they should be able to order one for you at discount prices.