You can try ParaWellness Labs, at least read his website. parasite testing is hit or miss and I am not sure how helpful this is in terms of resolving the problem. By that I mean that doctors are not equipped in treating this for the most part. Generally they will follow the guidelines of known remedies which for many is not enough in terms of duration or getting the right drug to target this.
Testing can be helpful in terms of identifying classifications. There are many types of pathogens that can inhabit the gut including bacteria, yeast, protozoa parasites, viruses and worm (flukes)parasites.
Worms are the only pathogen that can show in the stool as far as I know, at the same time I have seen many images that do not resemble known worm or fluke parasites.
Worms have tapered heads or tails, tapes dispense their eggs in the stool so people report 'white rice' in their stools while flukes are reported as 'rolled up tomato skins'.
It is important to support the body with nutritionals during these events. Porphyria is thought to be a problem with toxins and the inability to get rid of them. The immune system produces strong chemicals that the body must detoxify.