Lowering brightness, saturation and contrast by 10 helped me a bit it was at 100% everywhere. If i wasn't allowed i used custom calming color scheme combo blueish-violet tint was particularly comfortable for me but I can only achieve this with Zoomtext Custom Color Schemes I could work with this much longer, much less eye strain and headache.

Pain meds will kill your liver on the long run they are big strain to this organ and they work for only for few hours. Any meds can have serious side effects, don't take anything without doc tests first. I take med which is used for migraine too but side effects are very common and not cool at all. My family member prefer cluster 3 day nightmare migraines 4 times a month over side effects every day of her meds. First diagnostic and non medication treatment is needed to be tried out.

Headache is common from eye strain and even dry eye I've been trough it. 8 hours of computer work is a lot for eye surface plus artificial lightning and no fresh air.
Do very frequently breaks, divert your gaze from monitor every 30-45 mins and look for 5 mins at something distant at best outside.
I tried artificial refreshing tears from eye doc it's temporary relief, don't forget to drink enough and regularly, i got special glasses (not blue light or computer cheap crap from eBay or Amazon) from optician it brought bit relief those have much better protecting spectrum than those available over Internet.

Learned and improved touch blind typing, oh that helped the most! Unconscious i vent over the keyboard to see the keys, i improved the technique. Straining neck and upper back muscular causes lot of headache. Some stretching durning breaks helps preventing it too.

When I was totally K.O i turned off the screen switched to JAWS or NVDA with screenreader and used Braille for a break to let my eye and head cool off instead of my mixed setup: Zoomtext with NVDA and Braille.
But overall simple tips brought me more relief than the glasses.

The only thing that helps for my migraines is Excedrin Migraine medicine. Works in 30 minutes!

UBRELVY can be a life saver if it is indeed migraines you are suffering from.

So I'm not an expert but here's what I've learned from working on a computer.

Use a high contrast theme that the easiest for your eyes. Personally, I use a green on black theme.

You could turn on your PC's blue light filtering feature. This does effect the colours displayed on your screen though, so if this is something that hinders you, you might consider getting blue-light filtering glasses.

Drink lots of water! General tip, but this could help combat your headaches and dry eyes.

Take frequent breaks. Every twenty minutes look away from your screen and blink a few times to lubricate your eyes.

Make sure you can read what you're doing without squinting. Change the font size/style to one that suits you best. Maybe consider purchasing a larger screen you can work on.

Finally, be super careful with painkillers. Increased tolerance and addiction are a real problem, so it's best to find ways that minimize their taking if possible.

Hope these help and good luck :)

I get light sensitivity that brings o. Migraines. Sunglasses, changing contrast and brightness also helps. For my migraines I micro dose entheogenic medicine which has worked better than any pharmaceutical.

Be really careful with painkillers many of them are adddictive.

Taking painkillers would be a bit like taking out the water from your boat with the bucket without patching the holes on it first. I recommend you a book called reach that for that, or they teach you a bit about passive income and diversifying income. Which I think is the only realistic thing to build for people like us who cannot stand alone time in front of the computer because of my strength