Hi.
Chesty cough with phlegm, fever and associated symptoms is suggestive of a severe
respiratory tract infection. I would advise you to get the blood, urine and sputum tested as also an X-ray of the chest to rule out
Pneumonia.
The main cause of such a voice change is
laryngitis, meaning inflammation of the vocal cords secondary to the upper respiratory tract infection.
The best treatment plan is :
First of all a strict Voice-Rest.
Decongestant Nasal drops followed by plain water steam inhalation.
A course of oral
steroids , antibiotics , anti-inflammatory and decongestant.
This will help you to come out of the present problem within a few days. Please discuss this with your Doctor and you may get a reference for an ENT Surgeon to get a Direct
Laryngoscopy to get a proper diagnosis and a prescription for proper treatment.