Degenerative Disc Disease Support Group
Degeneration of the intervertebral disc, which is often called "degenerative disc disease" (DDD) of the spine, DDD is in fact a condition that can be painful and can greatly affect the quality of one's life. While disc degeneration is not a normal part of aging and for most people is not a problem, for certain individuals a degenerated disc can cause severe constant...

As I understand your specific problem, you are concerned that 5/325 of Oxycodone is a reduction in medication from your previous Rx of 5/500 hydrocodone. Oxycodone is considered a stronger medication than hydrocodone, although it is possible that your body is not responding as well to oxycodone as it did to hydocodone. IMO, the small reduction in acetaminophen should not be as noticeable as you have written, so therefore, your problem probably is elsewhere. Either your body works better with hydrocodone than oxycodone, or your medical problems have gotten worse.
Also, if I understand what you have written, you have been taking opiate pain medication for many years. It is very possible, that your body has built up a tolerance to codeine-based drugs and you may need to be switched to a morphine-based drug, or something else.
There are several possibilities to consider. You need to discuss your current problems with your doctor. There probably was a reason your new doctor switched you to oxycodone. If it was me, I would expect (but not suggest) that your doctor will either move you up to a 10/325 pill of either of the two medications written about here, or move you to something else totally different.