what symptoms did you have before you started medication?
I see in your other thread that your TSH has been 1.85 for a while.
Have they run a Free T3 test lately to see how it compares with your Free T4?
Maybe you're having trouble converting T4 to T3.
Or maybe it's the adrenals?
Maybe Synthroid is not agreeing with you. Maybe you need to try one of the alternative replacement drugs.
How often are you getting bloodwork done?
Call the clinic and request they provide you with copies of all the thyroid blood tests for the last eighteen months, and see how "normal" the results are.
Labratory refference ranges vary, but the lab limits for TSH usually run between 0.3-3.0 or 0.5-5.0, depending on the particular lab.
Right now my lab is using a TSH lab range of 0.34-5.0.
Your TSH needs to be anywhere from a little under 1.0 to maybe up to 2.5, but probably around 1.5.
If your TSH is 4.2 and you need it to be 1.5, you fall within normal lab ranges but you are Hypothyroid.
But if there is not a flag next to the test indicating high or low, the doctor may leave you at 4.2.
You need to find out what your test results are, and see if your meds need changing.
You could also have a cortisol test run to check your adrenal function. Adrenal Fatigue has a lot of the same symptoms, and your thyroid also regulates your adrenals.
Hope this makes sense.