perhaps advised you to go to rehab because quitting this high dose of oxycodone
abruptly can be expected to result in strong withdrawal symptoms
which would be easier to manage if you are under constant medical supervision. If going to rehab is not an option, then rather than quitting this abruptly, try reducing the dose of oxycodone gradually before quitting. Go very slow, not more than 5 mg per week, and even slower if you wish. Keep yourself hydrated. Use over the counter medicines if there are mild withdrawal symptoms. And above all, remember that one may easily die from opioid overdose but not from opioid withdrawal
Hope this helps you. Best wishes.