Take anti-thyroid meds such as PTU or methimazole. That'll slow down that pesky metabolism problem.
Really kid, im assuming you are a kid, sorry if you are not, but, all you need to do is be patient, eat more quality calories, get lots of rest, and do some type of
cardiovascular excercise such as walking a few miles a day for example (vs jogging).
Other than that, your metabolism is what it is. You are born that way. Unless you alter it with drugs, it wont change most likely. Thank your thyroid gland, and your parents. Most likely,
one of them is hyp/hyper thyroid....