please post all your lab results including the reference ranges.
Question: Have you been tested or have you been diagnosed with Hashimoto's?
Hasi's is the #1 cause of low thyroid. It is progressive. It is an autoimmune condition that attacks your thyroid gland and over time results in the gland to produce less and less thyroid hormone. Which would mean over time in order to feel well, you will have to increase your dosage of medication to make up for that lost production by your body.
You do not list the reference range for the Free T4. But assuming that it is similar to what we normally see. You will be at rock bottom of the range if not even below range. Which indicates that you are undermedicated.
Other questions:
What symptoms do you have?
How long have you been on medication? And how long with this latest dosage?
how are you taking the medication? That is on an empty stomach and separated from taking vitamins' especially Calcium which dramatically will reduce tha absorption of T4 medication.