How do i know if i have fibrillary glomerulonephritis or immunotactoid glomerulopathy?

Complicated question: Definitive diagnosis will require renal biopsy.

Tough call!: I'm going to assume you've had a renal biopsy and there's a difference of opinion among the pathologists who have examined it. The two lesions look very much alike, and i'd urge you to request it be examined by as many of us pathologists as your lab / personal physician can find. Immunotactoid has tubules; fibrillary does not but some pathologists still consider it a subtype of the other.