Oxycodone is a pro-drug, meaning it's dependant upon being converted into something else in the liver to actually relieve you pain. Because of this, it can induce it's own metabolism and be effected by other drugs which have an effect on the P450 enzyme system in the body. (Which is 90% of medications out there).
You may find that certain antidepressant drugs in particular make
Oxycontin *less* effective. I know this goes against the current so called wisdom of medical practice, but most of them are schooled in voodoo and not chemistry. <G>
Taking Oxycontin (Or MScontin for that matter) 3X a day is not uncommon.
If he wont write it 3x a day, perhaps he will give you a substantial breakthrough medication dose and allow you to use that to get through the hump. They make Roxicodone in a 30mg formulation... Or perhaps
Percocet 10/325 if he will write you several of them.
Are you numb yet? No. AARRGGGGGHH! I told you I wasn't numb! Sorry, I didn't believe you.