Did some fps searches in google and ended up here haha, since I'm not a stranger to the forum, I'll make a quick post.
Type the following in console:
fps_max 100
^ See if the above makes a difference. Some say it helps but not for me. But yea it wouldn't hurt to set it and leave it to 100 maybe you'll get lucky and it will boom up to 100. I get around 30 to 50 fps and I go against people with 60 to 70 and I own. It's a matter of strafing and controlling your recoil. From what I've heard, the human eye can only see to 70 fps and no more. I never saw 100 fps before. Having vsync off is a good thing, afaik. I've never heard of anyone leaving it on.
If your fps drops and changes from 10 to 40 to 20 to 70 then that's normal gameplay. You can not have a SOLID 50 or 60 fps as far as I know. Sometimes the location from where you're playing affects fps too especially latency, so try playing at a closer zone.
Also you said that your eyes hurt when you play? How does fps hurt your eyes? I think you're talking about the high latency(lag spikes) that your're getting????
If that's the case then type the following in console:
cl_cmdupdate 101
cl_cmdrate 101
rate 20000 (default is 9999 I think)
^ Try the above and see if it helps your lag issues. For most people it does. If not then you can either leave it as is or reset it back to default.
You can try setting your display(screen resolution) to the max instead of 800x600. Oh yea and go over to your control panel/display/settings and set it to 16bit instead of 32bit, see if that helps.