It does sound like withdrawal symptoms from oxycontin. If he gets bad enough he can take a small amount to relieve the symptoms. But it would have been a lot better if he had the doctor wien him off of it. He should never break one in two to wein off because they are time released and he would get too much medicine at once.
Can you talk him into calling his doctor and have him help him. You really can't force him to do anything but you could suggest it. Going cold turkey isn't a good idea.
I wish you luck with this,
fibromyalgia, Chronic fatigue, depression,allergies