I was prescribed 200mcg Levothyroxine post completion and RAI. TSH was undetectable and I felt dreadful. Dose was decreased in 25mcg until I was on 100mcg but had gained fibromyalgia, COPD, parasthesia and a host of other debilitating symptoms. TSH was then 0.03, FT4 low and FT3 below range. Endocrinologist wasn't concerned and dismissed me for six months.
I added T3 which lifted brain fog and alleviated some symptoms temporarily. I was convinced it was a reaction to a build of Levothyroxine and stopped it. Two months later I also stopped taking T3. I felt so ill and was mostly bedridden I could only hope that clearing my system of all meds would help. a detox, if you like. I was suicidal and didn't much care if cancer recurred.
After two weeks on no meds I could breath, parasthesia, internal tremors and debilitating palpitations stopped and I could sleep. A lung function test (spirometry) showed I had 97% lung function (six years after quitting smoking). I continued off meds for 4 weeks in all but was bone crushingly exhausted and cold so resumed on 100mcg Levothyroxine. TSH had risen to 107.5 but I still felt better than when on Levothyroxine.
Palpitations resumed after 7 days and tremors returned so I reduced T4 to 75mcg and added 25mcg T3. This seemed to do the trick for me and was the beginning of my recovery although my TSH was 0.16 and no suppressed.
In February the endo agreed to prescribe 20mcg T3 in addition to 75mcg Levothyroxine after I told him that I preferred to have some quality of life now and would accept increased risk of cancer recurrence and pointed out that T3 suppresses TSH so it may not be a risk after all. In March I hit a wall when I increased activity and upped T4 to 100mcg and was able to tolerate it. In April I'd become more active then hit another wall and increased my T3 to 30mcg and increased again this morning to 40mcg.
I'm not suggesting you stop medicating but it is recognised that many patients do require T3 (Liothyronine) in addition to T4 after total thyroidectomy and T3 also suppresses TSH to avoid recurrence of cancer. If you aren't converting T4 to T3 increasing your Levo is only going to make you feel worse.
If your GP won't prescribe T3 you can buy it online. PM me if you need a source.