I agree with the others. Going on a "drug holiday" can make a difference. My PM puts me on one once a year and it has been pretty good. There is research out there that says that many conditions can be managed by a consistent level of medication if tolerance is appropriately managed. But as PA points out, that doesn't apply to all conditions. Some actually do get physically worse & that's what contributes to needing more meds.
Also, if you are taking the prescribed amount your doctor gave you, I would suggest that INSTEAD of going to a rehab facility, that you have the holiday managed by your PM. S/he would better understand how responsible pain patients react to withdrawal. Detox centers are just used to people who are looking for more drugs (with a few exceptions). Your PM would know to give you more meds if somehow you have a horrible, horrible pain experience when cutting off or cutting down on your meds.
Also, as others have pointed out, your PM will check to make sure you are healthy enough to go off them completely. Some people (like me) have a hidden health issue & cannot cut down as quickly as others. I have an extra heartbeat. It is not really ever a problem except when I am cutting down to quickly from the pain meds. So we just go a little slower. And if needed, sometimes he will just switch me to a different medicine for a while, or just cut me down pretty low, rather than cutting me off completely.
There are responsible ways to manage tolerance & your doctor should be able to help you. Plus, there are meds to help you cope with the withdrawal symptoms.
Please do have a thoughtful discussion with your doctor about what your options are. Almost every PM out there is happy to help their patients who want to manage tolerance do so. Also, sometimes medications that have worked for years just aren't effective anymore (this happens even with anti-convulsants, anti-depressants, etc.). Maybe it's time to try a new med.
PS -- Yes, they can disclose your status to your doctor in some cases. Rehab centers often assume that you are there b/c you are an addict & that informs many of their decisions. I have heard of people who are not able to get any more pain medication ever after visiting a rehab place.