When I withdrew from Oxycontin, my dosage was reduced every third day......so it seems to me that one of the reasons that you are still feeling so lousy just might have to do with the length of the tapering.
I'm not surprised that you aren't suffering nausea or any of the typical side effects of withdrawing because your taper is so drawn out, you are barely reducing a milligram over a 10 day period.
It also does not surprise me that mentally it is tougher for you, since again the tapering is being done so slowly.
If I were you, I might talk to my doctor about speeding up the tapering so that you are off the Oxycontin once and for all, then you can make an assessment about where your pain level is and go from there to other options if necessary.
Sometimes, I think the mistake that some of us make is having a taper go too slow or too fast for what our bodies can tolerate. Most people can handle a reduction every three days or so , without experiencing too many negative side effects of withdrawal. Especially when the meds were used in a chronic pain situation.