Hello Cough with expectoration ( phlegm ) from white to yellow in color , cough worse in the night and early in the morning ,may be due to these possibilities , these include. 1 Asthmatic allergic bronchitis :Airways hyperresponsive that is secondary to inflammatory disease that results in recurrent or chronic episodes of wheeze, shortness of breath chest tightness &/or COUGH particularly at NIGHT or in the early in the MORNING ( as these few symptoms present in you). Diagnosis can be confirmed by physical examination by a physician and clinical examination . 2 Bronchiectasis .Defined as localized irreversible dilatation of the bronchi. .Condition results in airflow obstruction & impaired clearance of secretions . Present with chronic sputum (phlegm) production. It may be mild in your case with these symptoms . Ratty cough producing sputum ( phlegm) after colds only. Sputum production of Change of position cause production of sputum, Xray chest and sputum examination will find the disease. 3 Tuberculosis :Diagnosis can be confirmed by X RAY chest and blood examination for C B C , E S R ( if 100 mm 1st hour strongly suggestive of chronic disease of lungs or tuberculosis ) . Also get in sputum for A F B examination. In my opinion deal as mentioned above. Hope this information will be helpful for you. Good luck.