The 5 mm spot on your lung could be cancer but the majority of nodules this size are benign. The best approach is to follow this spot with repeat CT scans. It probably has nothing to do with your shortness of breath.
There are many causes of shortness of breath and asthma is one of them. Perhaps your doctor heard wheezes. You should ask him/her. COPD, from cigarette smoking, is another cause. So are clots to the lung.
If all your lymph nodes, including the large one in your armpit, are shrinking it would be appropriate to continue to observe them. But, if there is any doubt or if one enlarges or if others develop, you should have a lymph node biopsy.