I'm not sure why your endo would give you prednisone to treat thyroiditis... Can you give us more information about your condition, such as what are your actual thyroid hormone levels? You should have been tested for Free T3, Free T4 and TSH; if you'll post those results, along with the reference ranges from your lab report, we can start there.
It would also be helpful, if you've had a thyroid ultrasound, to post the results of that, along with any antibody test results you've had that might indicate Hashimoto's or Graves Disease...
A list of symptoms would also be very helpful.