I was struggling because of terrible eyesight, and the ergonomics. I used to have an IPS monitor that used to fatigue my eyes a ton.
I also have a cheapo Cherry MX Blues (TVS gold) and a Logitech G402 mouse. Ergonomics and eye sore was killing me.
I sold off that monitor, got a decent 24in 1080p LG monitor with a TN Panel with VESA compatibility, Height extensions and boom all the eye fatigues have basically gone along with the shoulder pain.
If you’re sitting on something crappy, a used high-end chair.
If you’re sitting on something nice, a convertible sit-stand desk.