Swiss Balls do NOT make good office/computer chairs. They are great for exercising your core stabilising muscles (assuming you’ve been taught how to use them), but require far too much energy to sit on for long periods, resulting in slumping, horrible posture after a while. Use a good office chair with a full length back and lumbar support (not “strut and pad” type), preferably gas lift. If you like, get off it periodically and do some core exercises on your Swiss ball.