I tend to get a bit dizzy and fatigued while at work sitting at a computer all day. taking breaks helps but it comes back. eye doctor said all is ok?

Common!: Sitting is fatigueing. Get up and move as much as possible. The refresh rate of a computer screen can give your brain a "blinky" feeling. Again try to take periodic visual breaks as well as physical ones. And make sure you have a good chair!

All is ok: Taking breaks fixation excercises artificial tears all help on the computer. Use of dry eye medications is sometimes helpful.