My husband has prostrate metastasis cancer.

My husband has had a cough and is coughing up phlegm the doctor put him on 3 days of antibiotics, this didn’t work so they sent him for an X-ray,the X-ray came back fine and no further action.  Here we are another few month down the road and still he is coughing and spiting up phlegm. He coughs when he eats and during the day and night.  He says its green and sometimes there blood in it.  Should I speak to the oncologist or go back to the doctors. I am his carer as well as his wife.