I HAVE BEEN ON METHADONE FOR ABOUT 4YEARS NOW AND HAVE NEVER HAD ...

I HAVE BEEN ON METHADONE FOR ABOUT 4YEARS NOW AND HAVE NEVER HAD A PROBLEM WITH WEIGHT MY ENTIRE LIFE.NOW I MIGHT EAT A SMALL MEAL A DAY DUE TO MY ILLNESS AND I EXCERCISE AS MUCH AS I CAN AND NOTHING WORKS. I HAVE A CHRONIC ILLNESS (with several operations) AND HAVE ASKED MY DOCTOR IF METHADONE IS THE PROBLEM TO MY WEIGHT GAIN. OF COURSE HE SAID NO POSSIBLE WAY.I HAVE ASKED TO CHANGE MY MEDICATION TO SOMETHING EQUAL TO WHAT I AM TAKING AND WAS TOLD THAT I WAS ON SUCH A HIGH DOSE AGE (160MG) IT WOULD TAKE A VERY HIGH DOSE OF ANOTHER MEDICINE TO BE ADEQUATE.I JUST WANT TO FEEL O.K AND TRY TO LIVE MY LIFE AS ELL AS I CAN WITH DEALING WITH A CHRONIC ILLNESS AND NOT BEING OVERWEIGHT JUST FOR BREATHING.HELP!!!!!