Most cases of changelings were not documented in great detail due to the fact that they still tortured and murdered a baby. So it wouldn't have been greatly documented. The stories, like I said before, seem to tell of children who are deformed, usualy around the face, and look fay like. So that could be unusual eyes and mouth. Possibly down syndrom. The other cases just sounds like a mother who can't cope and claims that the baby never stops crying and she feels tired and drained all the time as though it is feeding off her, these are normal complaints of a woman who devolps a form of dissattachment due to post natal depression. So looking throuhg these cases, seperating the explainable cases from the unexplainable should give you a small amount of stories that could be true. But I think if you found that your baby was a changeling and you would never see your true child again unless you could strike some sort of deal you would keep it pretty quiet and undocumented, atleast until you and your child were old and safe enough.