What Can I Do To Get Rid Of This Bad

Brief Answer:
further evaluation needed...

Detailed Answer:
Hello and Welcome to 'Ask A Doctor' service...
I've gone through your query in details...
I can understand your concern...

Well, even a lot of medications (especially some antibiotics) itself can give the metallic taste as an aftereffect...However, their effects are self-limiting (means once the course gets over, these after effects also subside within a matter of time)...

However, considering your medical history, persistent cough for three weeks, despite treatment, need to be evaluated further (preferably under the supervision of a specialist i.e. Pulmonologist/chest physician).

As of now, for symptomatic relief, I'd suggest the following:

-Start doing Chlorhexidine gargle twice daily and lukewarm saline gargle twice daily in an alternate fashion...avoid going to any overcrowded places for the time being, if at all you need to visit, then use a face mask.

-Take some steam inhalation twice to thrice daily, it'll help to ease the associated symptoms to some extent and clear the secretions/drainage (if any)...

-Avoid any form of cold-drinks, dairy products and sour foods as they can further aggravate this situation...

-Please drink a lot of fluids. Have plenty of warm liquids (soups, broth, porridge etc.), they'll act as an immunity booster and fasten the recovery.

Ideally, a thorough set of investigations i.e. Hemogram, ESR, LFT, U&E, chest X-ray along with sputum gram stain, AFB and culture sensitivity along with a Pulmonary Function test (PFT) should be done to look into it in details.

Please discuss this with your doctor and proceed further.

Let me know if I can assist you further.

Take Care
Kind Regards

---