It sounds like that you suffered from computer vision syndrome. And getting eye strain from working at computer is very common. Don't worry, take a break when you feel eye strain, It is OK and harmless. Besides, if you didn't get good sleep last night, you may get eye strain easy when you work. In addition, people with myopia or hyperopia tend to get eye strain easily. So, personally, you'd better see an doctor and get an eye exam to make sure your eyes are in good condition. Good luck.
In common, people work at computer require intense use of the eyes. They need to focus on computer screen all the time that lead to eye strain such as dry eyes, burning eyes, sore eyes, or watering eyes etc. So, it is really common for you to feel eye strain if you continuous work at computer. If you want to get rid of eye strain, you'd better stop your work and take a good and long rest for your eyes.