Just as you said, you say you use computer screen too long, this may be the reason why your eyes hurt when you are tired. Seeing the computer screen for a long time is really bad for your eyes. And this may cause your eyes dry and a little pain and your eyes may feel very tired and sleepy. If you have to work in front of the computer for six to eight hours, you are supposed to have a rest for every two or three hours, such as having a cup of coffee, going for a little walk, going to the washroom.
Second, adjusting the brightness of the computer screen, the screen font and digital like the small bulbs which directly hurt your eyes.
Therefore, you need to have a reduction in the screen brightness. What's more, doing eye exercises is also a good choice to give your eyes a rest. If you want to continue your work, you can go to the hospital to have an eye exam and ask for the doctor's advices.