to prescribe natural desiccated thyroid which contains mainly T3 (which is what the body uses
) T4 and lesser amounts of T1 and T2 as everything works better in synergy
If after a while this is still a problem, your thyroid function could be tweaked with a trial of T3 only (cytomel).
If your new doctor is not familiar with all this, let me know.
Your low ferritin is indicative of likely iron deficiency, which could also impact B12 levels, thyroid function and digestion.