Worms are not microscopic ROFL! They are multicellular organism in other words can be seen by your eyes. You confuse helminths/worms with protozoa parasites to begin with. And because worms are a multicellular organism you can feel them while you can't feel protozoa.
You can feel parasites esp roundworms travelling around because of their body structure actually. But when one feel them he feels parasite larvae most of the time.
They can and do travel outside of intestines and it's not so uncommon. Just type in Google: Bugs under the skin. Now you have an idea how many ppl might be infected and have no clue what it is. Ppl just can't explain this and the general medical community stuck in the stone age regarding this infection.
Biting can be explained. Your WBC do chase parasites and try to take them down when they do that parasite divert WBC into repair by damaging your tissue/biting so WBC forced to go into repair mode instead.
So funny it's you who is ignorant. But instead of learning immunology with parasitology some ppl here prefer to talk BS instead about the subject which they don't even understand to begin with or take few bits out and think they know it all.
Now some ppl will be delusional and blame everything on parasites. But don't sweep all in one basket! That's what the medical community has done.
What we know today regarding parasites range in about 10% of knowledge. 90% still need to be explored and figured out.
With parasites it's anything but the common sense.