I'm not sick of computers at all :P I do get tired sometimes though.

If your eyes get tired, you might want to look into getting some reading glasses. After years and years of working on a computer all day, then going home and spending another few hours on a computer and wondering why I was constantly popping painkillers for headaches, I got my first pair of reading glasses a few months ago. My headaches are now stress-related rather than induced by eyestrain, so that's a victory for me. I'm only supposed to use them for work on the computer/reading/playing handhelds, but I've started wearing them around everywhere if I know I'm going to use them. Kind of a pain to keep taking them off and putting them into the case.

But yeah, if you can afford it you should get your eyes checked and see what the optometrist recommends. My 'vision' according to the test is actually 20/10 (which is 'better than normal'), but when I got hooked up to this machine it was discovered that I have Astigmatism. The Astigmatism is what was causing the eyestrain (and thus the tiredness/headaches), since my eyes were working overtime to focus on the screen. So while your vision may be perfectly normal, if you do have Astigmatism it probably would make your eyes tired faster if you do intensive eye-work for a long time.