Hello Persistent cough since 2 months ( dry ) but cracking sound present . You took amoxy & erythromycin . As these both antibiotics are very useful in respiratory infection but you didn t got relief , this is a cause of concern. The cough ( such type ) may be due to these reasons, these include: 1 Asthmatic allergic bronchitis because you are a smoker ,hence such type of cough may be due to allergy and this causes bronchoconstriction , hence there develop cough and this type of cough usually didn t respond to antibiotics . Diagnosis can be confirmed by physical as well as clinical examination by a physician. 2 Tuberculosis , this is also most common cause . As you mentioned that there is a shadow in X Ray chest and elevated E S R . So these two tests are an indication of tuberculosis . Get in sputum (if not present nasogastric tube will help ) .If necessary get in protein purified derivatives(PPD)-Tuberculin Skin Test. If necessary get in bronchoscopy for confirmation . 3 Cancer as you mentioned that there is a density in lung so we can t rule out cancer . Get in M R I for confirmation. However there are so many other reasons of such cough but deal as mentioned above . In my opinion consult a PULMONOLOGIST and get his opinion.