I'm not sure about methadone but I did cold turkey from suboxone and I've heard they're similar. There were a few things I was told to such as taking a really good multivitamin. Potassium, iron, and good vitamin c! Like the vitamin c packets. Epsom salt baths helped immensely! Rest, rest and REST!! Motrin 200mg 's 3 for sure. Are you alone in this or do you have any help?
Sorry to say but it’s going to last awhile. Took me over 8 months before I felt normal. I was on methadone for almost 10 years. I’m sure recovery time is different for everyone that was just my experience good luck to you stay strong it will get better I promise you that.