The symptoms you describe are not classic for GBS. It is true that there have been outbreaks of GBS after the flu shot. However, the fluctuatign symptoms, and muscle fasciculations would not be typical. Typical GBS has a slow steady decline in fucntion. Therefore, if you did have GBS you stated your symptoms are improving already which is good. The FLU shot can cause inflammation within the body which can manifest as aches and pains, weakness, and overall fatigue. If the symptoms continue then I would have this re-evalauted, including looking for lupus and other connective tissue diseases. Good luck.
Thanks.