Google “Horsehair Nematomorpha human diagnosis”. Or something to that effect. I have this (absolutely no doubts on that) & periodically I deal with what you describe to a “tee”. Actually had them today. They are definitely worms. My skin and muscles are riddled with them. I take Bounce Dryer Sheets and run them along a small area of my arm/hand/face/wherever, then hold the sheets up to the light and I can see the ones that move freely are in fact the worms and not the threads of the sheet. Some will thread themselves within the sheets and painfully re-enter me if I accidentally grasp them. They get pretty doggon aggressive with this. Good Luck to all on this thread!