The most common cause for the sinusitis
is viral infection but it generally becomes all right in 7 to 10 days.Sinusitis which is present for more than is generally due to bacterial infection but can be caused by fungal infection
.Sinusitis due to fungal infection can take place in diabetics or in people having low immunity as in AIDS.
You can go ahead with an antibiotic course of AUGMENTIN
625 mg three times a day along with steam inhalation twice a day.AUGMENTIN is supposed to be one of the best antibiotics for bacterial sinusitis and is taken for 5 to 7 days.Consult your doctor for it's prescription.
If you still don't become all right,then best would be to consult a ENT and get a possible CT scan
along with sinus endoscopy
and tissue sample for culture and histology.