I've had this and I don't know what caused it. I assumed it was pinworms since I got relief from taking lots of pyrantel and doing colon cleanses.
It will take awhile to get under control. I thought it was gone at one point, but it came back several times, so now at the first sign I will immediately start taking pyrantel and supplements to clear out my colon. I've never tried it, but I wonder if Liver Flushing would help? I've never used ivermectin, but it's broad spectrum so it should help. I've also heard doxy is important to use in conjunction with some rx meds because it will kill the bacteria that is released when the worms are dying.
I feel for you and you are right, it's hard to concentrate on anything else. I wanted to rip my skin off. :-(