so.....
You probably know that your thyroid produces T4 (and a tiny bit of T3)
T4 doesn't do shit for you so you body then converts T4 into T3
When you body senses low levels of T4 in your body then it sends out a signal TSH to produce more.
Do you have your TSH reading?
TSH is like stepping on the gas in a car. The higher the TSH then the more TSH your thyroid should produce. But if your thyroid isn't working well then it may not produce enough T4 even though you are producing enough TSH. (just like if you press on the gas but have a bad motor in your car then your car might not speed up much...)