having hard time weaning off oxycodone

69 yo male on 30mg pill oxycontin and 7.5mg pill oxycodone for 1 1/2 yrs due to back pain. just had surgery 12-7-10 and pain has been gone for couple weeks now. i was taking 3 or 4 of the oxycontin a day and 7 or 8 of the oxycodone a day, would taper off when months supply was getting short so would last til my next prescription. have been trying for week now to wean off the pain meds, havent had a oxycontin since 0500 on the 21st over 36 hrs, but cant seem to go below 3 or 4 of the oxycodone, i get real nervous and shaky at about the 7 or 8 hr mark between pills. i have had 3 oxycodones today, 1 at midnight to sleep, 1 at 0545 for more sleep and just took another 1 at 1315, was reall shaky. would cutting the oxycodone pill in half so it would be 3.75 mg work, or would that be too weak to take the shakes away?