Guillain-Barre Syndrome appears within few weeks after respiratory or gastrointestinal infection. So, the infection in 2003 did not caused the symptoms you experienced recently.
The symptoms you experienced are related to a neurological disorder. The tests you mentioned are indicative for different causes. The lumbar puncture was done to check for bacterial or viral neurological infection. MRI and CT scan were done to check for tumor and possible damage after hemorrhage or infarction. The only test that was not mentioned and might be recommended is Electroencephalography to check for functional brain disorders. These do not require morphological changes of the brain, thus making them invisible for MRI and CT scan. Instead small functional abnormalities of the brain cells might be present.