Regarding your first question, lung cancer is most commonly asymptomatic in the early stages. More advanced stages of lung cancer can be associated with cough, bloody sputum, shortness of breath, pneumonia, weight loss, and decreased appetite, among other symptoms.
As I am not sure what is upsetting your stomach (or what these symptoms are, exactly), I'm afraid that I won't be able to answer this question.
Sincerely,
Robert A. Wascher, MD, FACS
www.doctorwascher.com
Author, "A Cancer Prevention Guide for the Human Race"