This is Dr. David
it sounds like you haven't taken very good care of your body.
smoking cigarettes and pot will cause irritation of your lungs and put tar and nicotine and smoke and carcinogens into your lungs.
you are probably feeling mucus plugs and airway irritation from your prior smoking.
you need to stop smoking and eat healthier and start to exercise to become healthier.
you can change your lifestyle
if you continue to smoke and eat unhealthy, you will end up with health issues, diabetes, high blood pressure, cancer
you can see a doctor now and get pulmonary function tests, CT scans again.
I bet they won't show cancer
but your doctor will again tell you to quit smoking and to exercise and to eat healthier.
let me know if you have questions.