I have been coughing producing salivary sputum for a month with symptoms of common cold. sputum smear negative.what am i likely to be suffering from.

PND: You might have post nasal drip from allergic rhinitis, an antihistamine such as Allegra or Claritin over the counter plus a nasal corticosteroids such as Nasonex (mometasone) might work. Elminating the allergen or avoiding it will be the ultimate treatment but can be hard.

Many possibilities: This could be mycoplasma pneumonia, adult pertussis, chronic sinusitis with post-nasal drip, acid reflux, etc. Suggest you see an ENT specialist and get this worked out. The more remote possibility is fungal infection or tuberculosis (things difficult to exclude). You obviously need an intelligent evaluation from a good clinician. Bon chance.