After my grandfather past away many years ago I began coughing up a whitish, yellowish mucous. This has been going on for a year or two. I had been taking care of him for over ten years. My grandfather had lung cancer & worked in chemical plants with asbestos. Since going to a doctor about 4 months ago, I was diagnosed with a staff infection. The doctor prescribed me with antibiotics. It went away & now it's back. I am still spitting or coughing up this flem. It gets stuck in my throat & drives me crazy. What can I do, is this dangerous?