Hello dear, thanks for your question on HCM.
I can understand your situation and problem.
First of all, no need to worry at all for
lung cancer as it is extremely uncommon at your age ( 14 years).
In my opinion you are having either
asthma or
bronchitis. As second hand smoke can cause both of the above.
And coughing with breathing difficulty are seen in both.
So better to
consult pulmonologist and get done PFT ( pulmonary function test ).
This will also tell you about severity of the disease.
And treatment is based on severity only.
You may need inhaled bronchodilators and antihistamine drug.
So no need to worry for lung cancer, consult pulmonologist and first diagnose yourself and then start appropriate treatment.
Don't worry, you will be alright.