A dry cough lasting nine months with every major test coming back normal often points to something routine scans don't catch: post-nasal drip from allergic rhinitis, acid reflux reaching the throat, or cough-variant asthma. Your new runny nose and mucus actually point toward the first of these.
Next Steps
Ask your doctor about a trial for allergic rhinitis, such as an antihistamine or nasal spray. Mention whether the cough gets worse lying down or after meals, since that points to reflux instead. A pulmonologist can check for cough-variant asthma if this doesn't help.
Health Tips
See a doctor again soon if you develop fever, weight loss, night sweats, or blood in the cough.