I Have Graves Disease But I Feel Horribly Cold Why

i have graves disease but I feel horribly cold why .I am facing thinning of hair,extremely heavy bleeding ,extra ordinary weight gain, dry skin, severe chills, I take thyroxin but my symptoms never improve,i also have zero tolerance for heat and sweat profoundly during physical work .i am wondering how is it possible for a person with hyperthyroidism to have the symptoms of hypothyroidism my email is iffat YYYY@YYYY