My Drs Have Done Thyroid Tests And I Was On

My Drs have done thyroid tests and I was on levothyroxine 200 mcg and going back to 2012 when it was normal but on the low range .462 2012, then 2014 .172 and 2015 .019 and recently I tested low at my request and they dropped to 150mcg a month ago but I’m am still tired not sleeping and heat intolerant, my Dr wants me to wait 3 months to test. What is a date range between tests and what damage could have been done living with low and nothing done