Hello, I feel the same.
I have 'vertigo' etc., and I feel like I have balance trouble. This isn't the case though, my balance is pretty good.
I felt like this a year ago also, but it went away by itself, after having visited an ear specialist who checked for labyrintitis and such. Now it's back though, since a few days ago..
The mental fog you describe sounds like depersonalization which might have been caused by the meds.
You might want to, if money allows, try a pain clinic that teaches techniques such as biofeedback and deep breathing and meditation. Some people have found they can significantly decrease the amount of medication they use through these techniques. Might not work, but worth a try, because on that many meds you're going to have a lot of side effects, especially the oxy, but not limited to it.
The Oxyxontin will do it. Unfortunately, many of the treatments for chronic pain increase the level of depression and anxiety in a person. I have an injury to my right (dominant hand) wrist in which I had to be on Oxyxontin and Vicodin for about a month. My anxiety SHOT through the roof! I was foggy and anxious. Make sure you are talking about these issues. You may also want to look into a therapist and/or support group. You are going through a lot and your mind is no doubt overwhelmed.
Hope this helps!