I'm not entirely sure. I am tempted to say fasciola hepatica but the long strands are on the outside and the dark strands would be on the inside of the species I would think. I'm no expert by any means.
Some of the anti parasitic drugs are pretty hard on your system, but other are more benign. Have you considered taking praziquantel for the heck of it and seeing if you get any relief. That is about the safest one I know. I recently went to Tijuana and kept a pharmacist number from there. I'm pretty sure you could get any anti parasitic drug you wanted except egaten. Let me know and hang in there.
David