Then it sound like a disseminated roundworm infection. You can try to ask for blood serology (elisa) for ascaris, toxocara, strongyloides, filariasis. You can be positive for any of these, or negative for all, meaning you are infected with another subtype. They test for only 1 type although there are many. Anyway, you can try reese's pinworm med to see if you pass anything in stool that might be a clue. Many roundworms infect your intestines as well, primarily, not only the blood. Here on the forum there are plenty of resources on treatment, should you fail with doctors. Just be persistent and dont let them tell you otherwise. Roundworms are dangerous when disseminated. Need to get on meds as soon as possible, to avoid too much damage to important organs. They drill themselves through everything and lay eggs all over the place, encyst and suck you out of nutrition. They can really mess you up. Hit them hard now before it is too late.