It all depends on the source of your pain and the type of pain you're having. First of all, you're already on an antidepressant, so I'm not sure whether you can even take another one, like Cymbalta, or Triavil. . and Triavil has Amitriptyline in it. So, if the Amitriptyline is working for you at all, I can't see a reason to switch to another one.
The Gabitril and Neurontin will only help most likely, if you're having nerve-related pain....