You may be having a refractive error
which is causing the symptoms of headache which gets shifted to many sites depending upon the amount of eye strain
you have had. You are required to get a vision and refraction
check up done and use glasses if there is some refractive error in your eyes. You can use some lubricating eye drops which will give you a soothing effect. In case, the pain is intolerable you can take some analgesics as and when required.