Get it checked out by a doctor. I've had a cough linger for months because a cold flared up my Asthma. Also, smoking can cause COPD and I think chronic cough is a symptom of COPD.
When I have severe post nasal drip, it causes my stomach to feel terrible and I usually can't eat much either. And the severe post nasal drip can make me cough quite a bit too. I also know that some viral infections can linger for weeks and cause post nasal drip, coughing, sneezing, etc. that seems like it won't go away. And secondary infections in the sinuses and lungs can result in lingering symptoms also.
Let us know what the doctor says. Good luck & take care,
Gluten & Sulfite Sensitivity, Multiple Food & Inhalant & Medication Allergies, Asthma, Gut issues (dysmotility, non-specific inflammation), UCTD (Lupus?), Osteoporosis, Anemia, Very Low Lymphocyte Counts (T-Cells & B-Cells), malabsorption/malnutrition, etc., and now possible Lyme Disease (Igenex Lab says IgM WesternBlot is positive)
Meds: Pulmicort, Injectable Vitamin B12, Herbs, Nutritional Supplements, Essential Oils, Homeopathy.