It may be a long shot but two labs worth trying Parawellness and also DGR Labs need a doctor to order that one though but in a few weeks they will be offering PCR stool test that can pick up DNA from tons of different parasites.
Also I've been sick with this s#it for over two years.
If you can ever get a diagnosis from one of the worthwhile tests it can at least give evidence of being sick and also offer some help on how to treat as you can go for more targeted treatments.