What kind of room are you in? Does it have any windows?
For your eyes’ sake, in helping reduce strain and eye-fatigue, you need to refocus your eyes frequently;
don’t have them focussed on 1-3 metres (3-10 feet) all day because you work in a small room all day.
So it helps if you have a window to look out of ocassionally, while you work.
Otherwise, go outside.
Check your posture; are you hunching at all? Even slightly, over many hours can cause headaches.
So keep that back straight.
Keep your feet flat on the floor and your knees at 90 degrees.
Every hour, no matter how stressed you are, no matter the deadline, no matter who’s with you, stop work, get off the chair and do some basic stretching.
Stand tall and reach for the ceiling and look straight up, too.
And don’t do as I do, do as I say!
You don’t get a body like mine overnight: – it takes years of neglect!
cheers.
Neil.