I have neck and back burning and arms and legs burning sensation. i'm always tired. having a hard time concentrating. stomach pain and headaches.

Paresthesias: Get an evaluation. You have several symptoms, but they don't all point to one diagnosis. You should have a thorough exam and some routine blood tests. If all of the tests are negative and you still have symptoms, perhaps you have anxiety - get that checked out as well if the tests are normal. Sometimes stress, anxiety, and depression manifest with multiple physical symptoms.