I am a medical marijuana patient and have been smoking only cannabis for over 3 years. I have recently switched over to a vaporizor. I have cut down my smoking significantly and now I'm coughing up sputum with black spotting. Whenever I smoke my chest gets really tight and I start wheezing. In my research I found that vaporizors eliminates the carbon dioxide and spitting up the sputum is healthy. Any advice would be greatly appreciated.