Also-- put a birth ball near your computer. Only go online when sitting on the birth ball. Try to substitute as many chair-sitting times as possible with the birth ball (while eating, watching TV, etc). Make sure your knees/legs are at a 90 degree angle, fill up the ball to the amount that makes this happen. Alternate sitting upright (good posture), bouncing, and as you get closer to your due date do more pelvic rocks and going in circles with the ball.
Above all-- NO reclining, EVER! Reclining is one of the worst things you can do for positioning. If you want to take a rest on the couch, lay sideways with lots of pillow support instead of leaning back. Investing in a body pillow is great!