My 4 month baby keep coughing

Since she is only 4 months old, it might be worth going back to the PD or polyclinic if the coughing continues or gets worse, just to be safe. Sometimes they can check if there is anything else going on like reflux or a respiratory issue that needs a closer look. Keeping the room well-ventilated and making sure no one smokes near her can help a little while you monitor her at home.