Not sure if this is an option for you but I was getting a sore back at work and I just had a workstation assessment completed by an occupational therapist. She made adjustments to my chair, desk and computer height etc, gave me some lumbar support and also some other tips for working during pregnancy. One was having the desk and computer height higher than you usually would, can't remember the theory behind it but I certainly feel better.

Hope you can find a way to work comfortably!