Mary, you should never get a flu shot once you've had Guillain-Barre symptoms. I can't get it because I've had a similar condition caused by West Nile Virus.
Myotonia Congenita is nothing like Guillain-Barre (MS is much more similar). There is no demyelination with MC.
This is a page from a law firm that handles Guillain-Barre cases related to flu vaccines. It shows how relatively common it is and gives some information about symptoms.
For the past 20 years I have used a homeopathic product called Oscillococcinum made by Boiron to prevent the flu. Even though I have been exposed many times, I have never had symptoms while using this every week through flu season. I use about 1/4 tube at a time. If I know I've been exposed, then I take 1/4 tube every day for a few weeks. You can buy it at any health food store and in many grocery stores and pharmacies.