Chronic fungal sinus infection? if so, then is my immune system bad?

Fungi in the sinuses: Decreased immunity (reflected by deficiencies in immunoglobulins, particularly in iga) is only one cause of unusual infections in common places. Other causes include certain chronic diseases (particularly diabetes, but also rheumatologic conditions like wegener's granulomatosis), various cancers (particularly leukemia), and medications (particularly cortisone).

Fungal Sinusitis: It depends on what kind of fungus? If it is invasive, then it is likely related to compromised immunity and it can be lethal. Mycetomas or fungus balls are related to chronic allergy (hyper-reactive immune system). Indolent fungal sinusitis, is the exception of being invasive but not immune-related. Only a highly experienced rhinologist can properly diagnosed and treat this condition.