If you are coughing up Green Phlem then you should see your Dr as you could have an infection, the same goes for chest pain and difficulty breathing. You may need a course of Antibiotics.
Apart from the usual medications for colds they will take their course and a cough can last for a number of weeks.
Boil a chopped up lemon and add some honey to taste. I like milk with a spoon of honey as well.
Hope you soon feel better,