Lack of Focus

I feel like utter crap right now. I have a headache so bad that it hurts to focus my eyes (yet I still came to work today). I find myself staring into nothingness for indeterminate periods of time, which is severely reducing my productivity. Then, I start thinking that there are people I work with who behave like this every day. Do they have headaches constantly? Or do they just get the stupid effects without the pain? I can’t possibly imagine living like this, even without the pain, every day of my life.