I've never had those kinds of experiences but Mark Lapierre (he's a member of this forum as well) wrote about somewhat similar experiences a while ago in his blog
(the link is directly to the relevant post). He came to a different conclusion than Erin but thought it worth mentioning in case you are interested in some alternative perspectives.
For what it is worth your terrors sounds horrific and I'm glad I've never had a similar experience! Take care.