Pain and feeling pain relief is not in your head, when one is a RSD patient. Keep your chin up, and realize that objectively, your doc is telling you what he knows to be true. RSD is not a black or white disease, or there would be more definitive tests to diagnose and treat this culprit.
Enjoy your pain relief moments, and don't worry about the stuff you can't control. You are not a malingerer, and your doc knows that,too. If he thought you were, you would NOT receive the blocks at all.