This forum is for pediatric endocrinology, not sure if you are under age 21, if you are an adult you need to consult with your adult endocrinologist who treated you. A repeat of your thyroid functions will help look at the problem, this should include
TSHPituitary and tsh
Tsh and free and total
T4T4 test levels. This is best interpreted by an endocrinologist as you have already had thyroid disease. Adults can have many other concerns that need to be addressed that can give you similar symptoms such as back pain or muscle aches so seeing your physician will help.
If you are under age 21 again pediatric endocrinologist can help and same labs-your dose is very small for someone who had the complete thyroid ablated and it is very very likely that you are hypothyroid-needing more synthroid. See your doc, get the labs done and see how the medication dose is working for you. With autoimmune disease like thyroid comes a risk of other autoimmune problems like adrenal, diabetes, parathyroid etc. An exam and history will help and appropriate blood tests can be done to rule these out.
Hope this helps, feel better!