It sounds like you have a B12 deficiency. It might be worth getting your DNA tested (23andMe.com) and running it through Genetic Genie to see if you have mutations that impair B12 uptake or recycling. I have the MTHFR C677T and MTRR A66G mutation that mean I require additional B12 and vitamin support.
I wouldn't personally want to go on hydrocortisone unless it was an absolute last possible resort. I was able to recover significantly with only vitamins and herbs.