Okay, I am not a Doctor yet... but do have some experience in this area.
From studies I've read, and a lot of whats been taught thus far in classes, behavior skills are the #1 cause of insomnia.
Sit down and analyze what your doing the 4-6 hours before bed
Are you eating less than 2 hours before sleep
Are you on a routine schedule going to bed at the same time
Being on barbituates, opiates, and ambien, you must be exausted every morning, are you taking any uppers such as amphetamines (ie ritalin) or do you load up on sugars and caffeine throughout the day?
How restless are your thoughts at night? This seems to be a preceeding cause of insomnia and that is not being able to turn your thoughts off.
Are you seeing a primary care that has you on all of this or are you seeing a neurologist or any specialist? What kind of injury/incedent has you on xanax and oxycodone?
Probably should hold off on the medical advice until you are qualified. Xanax is a benzodiazepine, not a barbiturate.