Why do I have teary eyes?

I have noticed that from the past few weeks my eyes are always wet ie teary. I usually have very sensitive eyes, since even while applying eyeliner, my eyes starts developing a tickling feeling and it ends up in teary eyes..I recently have itching too in both my eyes for which i have applied eyedrops for 3 days. Its ok now. but my eyes are still wet. i have to keep wiping it every 3 or 4 minutes. I work in front of comp. for nearly 7 - 8 hrs straight with break for 1/2 hr for lunch. Is it becoz of it? Has anyone experienced this before? Pls. help..My face looks very dull due to this...