I have heard (don't know if it's completely true) that some people just don't respond to certain thyroid meds. For example, some people respond well to natural thyroid, but not synthetic.
Maybe you should look into something like Armour thyroid, which is T3 and
T4 in (I think) a 1:4 ratio. Comes in various different sizes (3 grain = same T3 in 1
cytomel). Armour is natural thyroid.