It isn't really 'purging'; it is just the body adjusting to changes in autonomic tone as the narcotic receptors slowly return to normal. Everyone has a slightly different withdrawal experience; so far I would say to count yourself lucky. By now you might be having a more miserable experience.
Opiate withdrawal takes from one to two months, for the most part. Methadone withdrawal is particularly lengthy, lasting for several months-- even six months after high dose discontinuation.
I would consider taking guaifenesin-- it breaks up mucous so that it is runny like water. You can take it with a prescription, or get it in robitussin expectorant. DON'T use the 'DM' or other forms-- they have other potentially psycho-active compounds. Just get the expectorant, and drink lots and lots of water.