What Causes Black Stool And Pricking Sensation All Over The Body?

Black stool, with what looks like small thin tiny white bugs/worms/eggs maybe with every wipe. They re there even if I m not having a movement. Also, every 2days or so I get these attacks where I feel as if I m being bitten all over my body and I ve many sores all over me. I went to dermatologist they said it was nerves and rx d me triamcinolone ointment. I put it on and w/in 2mins the biting feeling starts (even using nothing this happens but not as severe) & I notice many many small black specs all over my body where the biting feelings are. It bothers me so severely ive soaked in CloroxBleach water with a scrub brush scrubbing like crazy for it to manageably subside, it even wakes me up from a deep sleep. I m the only person in my household who s suffering like this. Please any ideas or suggestions??