Should I be worried about emphysema at age 19/20?

COPD... There is a form of COPD which can occur at a younger age. It is called alpha-1-antitrypsin disorder. It is caused by an enzyme deficiency and treatment includes enzyme replacement therapy. It is diagnosed with a blood test. See your doctor, or a lung doctor, for diagnosis and treatment if this disorder is suspected.
Only if you smoke. Or if you have the genetic susceptibility called alpha-1-antitrypsin deficiency. In any case, if you smoke stop. Emphysema generally begins to be diagnosed at age 40 and older.