dear user about your question i would like to tell you that chronic hedache has many causes and simply we can reach the cause of your son hedache by simple steps....first cause of hedache is stress and anxiety and sleeping disorders and you should observe any emotional or psychological troubles your son has as it is common between children....second cause that we may role out is anemia and poor nutrition because anemia cause severe fatigue and hedache and should be managed if present...third it may be brain vascularity disorder and you made ct scan so we can role out that if ct is normal...other common cause of chronic hedache is visual disorders or photobia and my advice to you to refer to ophthalmology clinic to chech for any problems with eye....at last you shouldnot get severe worry of that and just follow these simple steps and try to relax your child and give him funny days to relieve of stress.......i wish you and your son happy life