I don't know. I have flukes and other stuf and I have trouble gaining weight too despite how much I eat.
If you can spend a little I'd recommend trying a test from Parawellness and if you can go to NY it could be worth a shot seeing Dr. Kevin Cahill tho results with him are mixed. At least with the stool test you can see if they find anything. The mainstream stool tests can be useless but with parawellness the doctor there examines the tests himself.