" parasites should stay near the food source, but Im not sure if that's really true. I got migration during a parasite cleanse, but they do not go back to their place of origin (i.e gut)."
To answer this, YOU ARE THE FOOD SOURCE! If parasites aren't "eating food" you become their source of food. This is the nature of parasitic life.
In order to survive, they must have a "source" to live off of. Therefore, when they migrate outside the gut there are plenty of "food sources" for them to feed off -- blood, tissues, muscles, etc. this is what makes them so insidious!