You really do not need to worry about these readings of your thyroid function tests
or the substancial weight loss
you had. It is part of the hyperthyroidism
you have and your doctor has prescribed you right medications. You will certainly gain some weight to make you feel better and your symptoms will also improve over time. If it doesn't happen your doctor will send you for alternative therapy called radioablation therapy to stop the excess secretion of thyroid hormone.
So please wait for a few more weeks and follow your doctor's advice fully. Take care.