When you find that your eyes get out of focus when you try to see something, you should doubt whether you get the eyes infection because of the invisible bacterium. You need to have the good rest for the eyes, not sitting in front of the computers for a long time. You should also use some eye drops to make your eyes get moisture and comfortable.
I think you have got strabismus it is a eye disease which caused by the imbalance of extra-ocular muscle, so you can't see the same things with your two eyes at the same time. But you won't feel obvious eye discomfort if your eyes inclination is not high. There is also another reason causing your eyes out of focus, your eyes are too tired to focus on a thing, giving your eyes enough time to have a rest is the best choice.
There are many reasons for your recent condition. This condition can mean that your eyes are suffering from strain because that you have spent too much time in front of a computer. Reading books or newspaper usually will not pose the problem. So you should have your eyes rested by shortening the time used before the computer or looking elsewhere for several seconds every 30 minutes when you are working in front of it. If your age is 40 or so, you should have your eyes tested to find whether you get presbyopia or astigmatism. People of this age tend to have problem like that, for their crystalline lenses have deteriorated in flexibility.