What is the cause of chilling? i have a cough for 3 weeks now!

Infection: This is probably due to bronchitis or pneumonia. You should be checked by a doctor. Good luck!

Prolonged cough: A chronic cough could indicate many things and should be checked out by a doc. That said, if you now have chills on top of the cough I would be worried about an ongoing disease process. Chills are the body's way to create fever- since u feel cold, then pile on blankets or shiver which makes the muscles release heat-- fever! Cough now with chills could be pleurisy among other things & needs check