Many parasites have different life cycles. Difficult to say without proper tests being carried out. Parasites, microbes, toxins, molds, etc you'll find it all here.
Like you, I have regular flare-ups which make me very ill. It may help if you list your symptoms.
If you're thinking of having samples done I'm sure RHRPlus can take care of that. You probably wouldn't get much results through your own doctor. From personal experience I've found these tests to be very unreliable. That's why I turned to RHRPlus. And yes, if RHRPlus find anything, you'll get pictures.