have the drs test you for the 10 most common virus and bacteria infections first.
once you rule that out, then you can get into parasites.
The thing with parasites is is almost impossible to get a diagnosis, you have to treat them yourself by using emperical methods. E.g. do a Liver Flush (the Hulda Clark one is the best) and see if you get rolled upp skin tomatoes, thats liver flukes, if you got that the drug of choice is fasinex (triclabendazole).
Sounds to me from what your describing is it sounds like a protozoa infection (have you lost alot of weight? do your symptoms gets worse when you ingest sugar?) if so, try this recipe:
go to ebay type in: empty capsules and buy about 100 of the 00 size (thats 2 grams each), fill them with salt and take 2 capsules 4 times a day for 3 days, all protozoa infections should be cleared by the 3rd day.