Sarah, This happened to my mum. She was on meds for years for Hypothyroidism and then we noticed she had a goitor. So she was rechecked and had developed Hyperthyroidism. She had to have the goitor removed and most of her thyroid. So she's on meds again. But the Dr said it was very unusual. But it does happen very occasionally. Her mum had the same thing many years ago. So can't be THAT uncommon. U r very special hon.....and I hope things improve for u....*hugs*