Hello and welcome – The experience with methimazole is very individual. Many patients end up doing well on a low dose, while others experience side effects or have issues getting stabilized.
One thought is whether you got a definite diagnosis of Graves’ disease, as you can have elevated T3/T4 and suppressed TSH for other reasons. (For example, the early stages of Hashimoto’s or an overactive nodule.) Antibody testing (TSI or TRAb) can help point you in the right direction.