Persistent dry cough, especially like those you are experiencing, could be due to a problem in the throat, rather than in the lungs. The throat may experience itching and irritability, leading to the cough.
This kind of dry cough from throat irritation may be due to a variety of causes. One of the most common irritation is from gastric reflux. This means acid in your stomach has refluxed all the way up to your throat.
As your throat is an exquisitely sensitive organ (you will know just from choking on one drop of saliva!), just a small amount/duration of acid irritation is enough to give you trouble the whole day long. This means, you may not even experience symptoms such as heartburn or acid brash, and they may start after a bout of binging foods that trigger reflux (such as lots of spicy, sour, oily foods during CNY, for example).
Other very common issues that can contribute to this irritation could be from post nasal drip from sinus problems, or throat dryness from persistent mouth breathing in cases of chronic nasal obstruction. This is exacerbated if you spend most of your time in air conditioned environments, where the air can be very dry.
To get rid of this chronic dry cough, you should have an ENT evaluate your upper aerodigestive passage. We can then assess whether your problems are from your sinuses, post nasal drip, obstruction or reflux and treat accordingly.