Hi Bigguysmom,
Welcome to the recovery forums. I'm so happy you found us, there are a lot of diverse forums here so you can get your questions answered and learn how other mothers cope in your same situation.
My drug of choice was not opiates, which is what they call your sons particular drugs. It is a very harsh withdrawl, however it doesn't sound like, from his story, that he was taking very much. I myself am an addict in recovery and so are most of my friends. One of the many lies an addict will tell you will have to do with the quantity of drugs they took and for how long. We just don't really know how bad the addiction was. I say addiction because if he was taking all of this pain medication without it being perscribed for legitimate purposes than it is drug abuse. Oxycontin is HIGHLY addictive. I suggest you go back through this particular forum and read all the threads on opiate withdrawl and abuse. Also read the threads about methadone. Methadone is usually perscribed for a person addicted to opiates because the withdrawl is so intense. However they often regret using the methadone because it becomes even harder to get off of that. Both of these types of threads will give you some insight into pain medications like you are referring to.
Also, I suggest you go over to the Naranon board and share your story over there as well. There are a lot of mothers in your same situation who have been dealing with this for years. Alanon and naranon are programs for the family members of addicts and alcoholics. You're going to need some support and information for yourself, especially if he move home with you. There are wonderful and supportive people on that forum that will welcome you.
Take care and god bless