I had the same problem as you, I couldn't read on a computer for more than a 15 minutes at a time, my eyes would hurt so bad, get headaches, etc.

Then one day I was on a flight and flipping through SkyMall and saw an ad for "computer glasses" that got rid of eye strain. i was like "yeah, right". But I was desperate, so I bought a pair, and I gotta say, it's been one of the best purchases I've ever made. I no longer have eyestrain, can read for hours online.

Here is the brand of glasses I got: http://www.gunnars.com/