If you use your computer for long periods of time, then you should get into the habit of taking a break to focus at distant ranges. Looking out the window is a great idea, but you should try to do it every 15-20 minutes. That exercises the muscles in your eyes.
Also, when you're focused on the computer screen or you're reading, you blink less and that causes your eyes to become dry and that would normally cause some blurriness. In your case, your contact lenses also dry out resulting in blurriness. In this case Artificial Tears or Lubricating Drops may be helpful.
A combination of both the breaks and lubrication should show some improvement.