어서 미치다

it's driving me crazy

A feeling plus -아서/어서 gives the cause, and 미치다 'go mad' supplies the intensity — almost always as 미치겠다 or 미쳐버릴 것 같다: 억울해서 미치겠어요 (I feel so wronged it's driving me mad), 너무 귀여워서 미치겠어요. It is pure exaggeration, nothing to do with mental health, and it works for pleasant feelings as readily as unpleasant ones (이기고 싶어서 미쳐버릴 것 같아요).

Register: casual and emphatic