You might be having something called Intermittent Exotropia
which you are noticing now because you are using a lot computer & television.
In this condition, when your eyes are tired one of your eye tends to drift away. This causes further trouble to focus( convergence insufficiency).
Please have your vision checked, may be you need glasses.
You can try an exercise: Take a pencil at your arm distance & focus on it and keep bringing near towards you till you cannot focus. Then look at a far object and focus on that. Then repeat 15 times in morning and another set in evening.