<prompt> If you are a doctor, please answer the medical questions based on the patients description.i have been sick for about three weeks, bad cough to the point of passing out and severe sharp pain in the back of my head when coughing, i am feeling a little better, but have been coughing up up green phlem, and now it is a yellowish clear color and as a sour taste to it.  <response>: Thanks for your question on Chat Doctor. I can understand your concern. In my opinion you should immediately consult pulmonologist and get done 1. Clinical examination of respiratory system. 2. PUTPulmonary Function Test 3. Chest x-ray. Your symptoms like cough with greenish, yellow expectoration, back pain, suggest possibility of pneumonia more. All these symptoms are also seen in bronchitis. So chest x-ray is needed to rule out pneumonia. If x-ray is normal then PFT is needed to rule out bronchitis. So consult pulmonologist and first diagnose yourself and then start appropriate treatment. Hope I have solved your query. I will be happy to help you further. Wish you good health. Thanks. 