That certainly does sound frightening! So terrible to go through something like that. Very unwise of that doctor. Medications are like band-aids, they are used to treat symptoms and many of them are dangerous. The basis is the need to clean the body out and feed it what it needs.
Cleansing the body and doing Doc's program is certainly something for you to look at doing. There is a lot of good advice on here. You can do a search about thyroid issues just here on Doc Sutter's forum. Lots of reading...try to not get overwhelmed. It is a different way of thinking. Getting away from the medications and doctors advice. Many of them are influenced by big medication manufacturers (big pharma).
My advice right now would be to not panic. Don't ever take that med again and start working on cleansing the colon first, clean up your diet, no artificial sweetners (they cause neuro symptoms just by themselves), lots of pure water to flush out the toxins.