Have they done a bronchoscope? They take samples and view for lung damage . I suffered with Shortness of breath and weakness for three years until my internal Med Dr demanded the pulmonologist did the bronchoscope after I was coughing up blood . By that time my lungs were already very damaged ! I had mycobacterium avian complex infection . It was also found in my sputum specimen . After 60 days of IV meds and 1 and a half yr of oral antibiotics and Ethambutol. The chronic bronchiectasis and lung damage is what I’m left with . Be persistent to get answers as the nodule formation is a tough result . I have an immune disorder and so I never had blood work that would indicate infection plus I did not have a fever but I would have cool sweats all night long .