Im 16 female and have hypothyroidism with a very high metabolism instead of very low. i take levothyroxine and have been treated since birth for it. but will i always keep the high metabolism for the rest of my life?

You don't mention what you experience as signs&symptoms of high metabolism. Do you eat a lot and not gain weight? Do you have a fast resting heart rate ? Sleeping problems or increased sweating? These signs & symptoms don't occur with hypothyroidism unless your dose of levothyroxine is too high. An endocrinologist can advise you further.