Helminths have distinctive tapered heads or tails and are generally seen with the naked eye. I did see juveniles under about 40x which was the lowest magnification of the scope. I would think that 40x would be the highest you would have to use for helminths.
With microscope detection, they look for the egg (ova) - the ova has distinct identifiers where the adult worm has many similarities to other worms which makes it difficult to distinguish.
Have you been to a ENT doctor to see if their lab can identify the pathogen? Worms are not the only pathogen or parasite that could inhabit. Could be protozoa, bacterial, yeast/fungal or viral.