Hi.
Noted your history of 
root canal treatment, found fungus in sinus. the roots of teeth in sinus.
One of the known reason for 
sinusitis is infected root of a tooth projecting into the maxillary sinus. 
You are a known case of such a reason.
Once a sinusitis occurs fungal growth is known to occur.
I would advise you the following in such a situation:
First of all consult an ENT Surgeon for proper clinical evaluation, examination and get investigated like 
CT scan of nose and 
sinuses, Dental X-rays.
You need a surgery for clearing the sinuses of fungal ball, remove the disease teeth completely, 
To work in unison with a Dental surgeon as there will be need of mucosal flap coverage for defect, may be 
bone grafting.
Take care. Hope I have answered your question. Let me know if I can assist you further.
Regards,
Dr. T. Chandrakant, ENT & General Surgeon