I am 28 years old, i have itching in my left ear only specially at night when i go to bed for sleep. its being 5 years i have this problem. i consulted ear specialist but he said everything is fine and gave me dexatob ear drops but it make worse?

Well the most likely cause is irritated dry skin in the inner ear. The drops likely irritated it more. The most common reason why it would get dry and irritated would be water from showering and getting in there and when it evaporates it dries the skin out. Try putting a few baby oil drops in your ear, at night, then cotton ball to hold it in and remove in the morning. See if this helps.