Such a difficult issue. Your doctor is obviously worried about addiction since these drugs can be habit forming. From what I've read addiction is rarely found in people who take high amounts of these drugs for pain reduction. Oxycodone is a very effective drug for some FM patients.
http://www.fibromyalgia-symptoms.org/fibromyalgia_opioids_contro.html
Addiction is a concern for him but you need pain relief and he should be focused on that. Perhaps his plan is to transition to other drugs as he brings the oxycodone down (?). If his plan is to simply reduce the drugs to what he feels are acceptable levels and then leave you where you're at then you should think of finding another doctor.
Good luck.