It is usually from unstable thyroid levels...normally Hypo.
As you have Graves it would be unlikely that your TSH would budge much (with a thyroid) and your FT4 is low and FT3 average to low with Graves.
You are basically heading Hypo with the antithyroid meds and time for your Doctor to decrease a fraction.
5/25/10 labs
tsh 0.022
t3 free 3.51 1.70-4.20
t4 free 1.01 0.70-2.00