Many reasons which may indirectly contribute to headaches aside from screen use which you can eliminate to narrow the diagnosis:
#1 Eye sight/power, a simple visit to the ophthalmologist might put you at ease.
#2 Balanced diet, sometimes we consume food which may not be the best in terms of gut health or maintaining acidity in our stomach, this in turn could cause digestive issues leading to headaches. (drink only two cups of coffee spaced 6 hours apart)
#3 Effective breathing, science has linked poor breathing and mental fog which lead to many physical ailments not restricted to headaches, so before you start working it's essential to prime your mind just after you wake up since the brain's neuroplasticity is at it's peak and ready to be tamed, so meditating for 20mins with deep breathing and expansion of your diaphragm could mitigate mental fog which could accrue throughout the day and also decrease afternoon drowsiness. Also get your sinuses checked for any air blockage.
#4 Sleep, make sure you are getting minimum 7-8 hours of sleep every single day, if you say work or family or any other excuse, that means you are not effectively prioritizing your time, no matter how much work or productivity you cram in a day, if you skimp on sleep, beta amyloid proteins get built up in your brtain leading to extreme brain fog or headaches and over many years you could be on the verge of experiencing severe dementia or Alzheimers.
#5 Emotional mindset, Are there troubling issues with your personal life that occupy your mind and not allow you to completely focus, this may seem benign at first but could be the symptom of a larger un-diagnosed emotional issue which can manifest in physical ailments like headaches, digestive issues, joint pains etc. Also Chronic Stress is one of the most leading causes for headaches among adults, so be mindful of your stress levels as cortisol in your blood can alter your mood and physiological states.
and few other factors like, dehydration, skipped meals, hormone fluctuations, and exposure to chemicals are common migraine triggers. Please take care and wishing you great health for 2021!