for 6 weeks requires several critical investigations.
1. If you are a smoker, then a ENT consult to exclude throat pathologies
2. Exclude communicable respiratory diseases like TB, especially if you have been in contact with someone with infection (active) or a recent visit to a country with TB
3. Post nasal drip
due to allergic or non-allergic rhinitis
can cause the same constant cough that worsens at night when you have dust mite allergies
If options 1 and 2 have been excluded, a visit to an Alergist for skin prick test or specific IgE blood test
can help find what your allergies are.....antihistamines (long acting) and nasal corticosteroids
for 6 weeks (minimum) is recommended.