This actually not from my specialty, but I would love to answer.
While taking thyroid hormone supplement, one should observe few facts. 1) tablet should be taken on empty stomach first thing in morning. 2) do not eat anything for at least 1 hour after tablet. 3) Be regular in medication and prompt in time. 4) try not to forget medication.
If You are already observing above facts, pls get your TFT repeated. Also u need Bit D3 supplemental, ask your doctor for same.
Hope this solves your problem