Welcome to the board.
I think your doctor would probably be the best to ask about the Methadone. I have dispensed it to Patients in the past and they were all very thin and had been on it for at least a year. Dosages may have something to do with it.
Whats in a coke zero? Is it splenda or aspertame? Remember you can only have 3 servings of sweetner a day. A clean induction is best for optinmal weight loss and no cravings. Read everything you can here to help you!
Try to think of options you can replace the old favorites with. Like decaf coffee and tea.The cravings will only be difficult for a few days then you wont even miss the old stuff as long as you give yourself other options you enjoy
Good Luck!