I have this same problem, which started when I was under a lot of anxiety and now I have GERD. I believe that a neurologist can also treat this - check it out and see. I know that GERD can cause hypersalivation. I have also read where low thyroid can as well. Have you also checked into an oral surgeon? Mine did go away the first time I had it on its own and then came back years later. My thoughts and prayers are with you for a solution. Let me know how you are doiing.