Try the following steps,
1.Pace a soft pillow as support to the lumbar spine when your at work in front of the computer so that you can sit erect.
2.Raise the height of the monitor so that it is in level of your eyes.
3.Rest your elbows on the hand rest of the chair and operate the mouse with a movement at the wrist joint only.
4.Take 5 minutes break every hour.