There are 3 very common reasons for chronic cough -- GERD (reflux), asthma, and post-nasal drip. It sounds like yours may be post-nasal drip, given that it is worse at the end of the day and better when chewing gum (you make more saliva and the back of your throat stays wetter). I would recommend trial of an allergy medicine or nasal spray.
you take ginger and lemon and cut in small pcs and take one pcs ginger after take your meal.
Hello, not sure if you are on any medications but if you are some medications can cause a chronic dry cough (some sort of allergic reaction). My mother in law suffered from this for about a year. Doctor couldn't figure it out until one day she thought maybe it was her blood pressure medication so they changed it and the cough went away. Just a thought.