I have also similar symptoms. I research long, at time I think it must be something like sand fleas, I've been thinking about everything, but I find nothing accurate, it must come from the insect, I think my dogs have also the same, even when them I have no diagnosis of vet. I took ivermectin, albendazole and praziquantel. on ivermectin I react with more movement of this "something". I have a dose ivermectin in mouth held for hours, so that the movement has reduced in the mouth, but movement on nack and other place I still have.
as it was in the breast, the breast was red and painful with very pronounced tunnels, which has since been withdrawn, now I have it in the face, just hope that it is regenerated again.
I have visited lot of physicians but I still without diagnosis- only ignorance, you have luck that your practitioner will take you seriously. Try to get a test for dirofilaria.