Chronic Obstructive Pulmonary Disease (COPD) Exacerbation: The patient's history of smoking, productive cough, shortness of breath, and wheezing are all consistent with COPD. The chronic nature of the symptoms and the recent worsening suggest an exacerbation of COPD.

Bronchitis: Given the productive cough and smoking history, bronchitis is a plausible diagnosis. It could be either acute or chronic, depending on the duration and severity of symptoms.
Pneumonia: Although the patient has been experiencing symptoms for six weeks, pneumonia could still be a consideration, especially if there was a recent worsening of symptoms or if the patient has a compromised immune system.
Asthma: The presence of wheezing and shortness of breath could suggest asthma, particularly if the patient has a history of allergies or if symptoms vary with time and environment.

Lung Cancer: Given the patient's age and smoking history, lung cancer is a critical diagnosis not to miss. Even though it might not be the most likely cause of the current symptoms, the potential consequences of missing this diagnosis are severe.
Pulmonary Embolism: Although less likely given the chronic nature of the symptoms, pulmonary embolism can present with shortness of breath and could be life-threatening if not promptly diagnosed and treated.
Tuberculosis (TB): TB can cause chronic cough and shortness of breath. Although less common in some regions, it's a diagnosis that should be considered, especially if the patient has been exposed to TB or has risk factors such as immunocompromised status.

Cystic Fibrosis: Typically diagnosed in childhood, but mild forms can present later in life. It's unlikely given the patient's age but could be considered if other diagnoses are ruled out and there are suggestive findings such as recurrent infections or malabsorption.
Bronchiectasis: A condition characterized by damaged, dilated airways, which can cause chronic cough and shortness of breath. It's less common and might be considered if other diagnoses are excluded and there are specific findings on imaging studies.
Sarcoidosis: An autoimmune disease that can affect the lungs, causing cough and shortness of breath. It's less likely but could be considered if other diagnoses are ruled out and there are suggestive findings such as lymphadenopathy on imaging.