@nikudy Sounds like potentially you might be experiencing the same problem I am that I describe in this post: Sick with new LED backlit PC monitors
I've been trying to figure this out for years and after extensive research and monitor testing I believe my issue is the backlight itself: new LEDs produce different color spectrum than older LEDs. (I once even found a new LED desk lamp that caused the same symptoms.) I can use older monitors (like the one you mention) all day with no strain at all, but any new monitor- including all NINE of the 27" 1440p monitors I've tried- significantly bother me within minutes (eye strain, "sick feeling," dizzyness, etc.). I am on a personal quest to find a gaming monitor I can tolerate. Please do let me know if you find one. 🙂