I�m 28 years old. What are the chances I have lung cancer given my history and present condition?

Age 28 - your chances of having a primary lung cancer are roughly the same as your chances of being hit by lightning. Ignore the answer about family genetics and lung carcinomas. Lung cancers are clearly smoking related, but 28 is too young for most. Stop smoking if at all possible. It is a difficult drug addiction to quit. Best of luck.