Chronic pain is very complex problem. The first issue is identification of the underlying cause. Treating pain without treating the underlying cause is fruitless. If the muffler off of your car, you can turn up the radio or fix the muffler. Turning up the radio, makes you unaware of the muffler problem, but you still have a bad muffler.
Narcotics will act on the brain and make one less aware of the pain, but does nothing for the actual cause of the pain. Demerol is a narcotic, and not a good one when needed in repeated dosing. When the body breaks down or metabolizes Demerol, the products of that breakdown are potentially toxic when the accumulate in the body. Other medication will act on various parts of the body to decrease pain or make one care less about the pain. Other therapies such as regional anesthesia or blocks should also be considered. There are other therapies that have effectiveness without medications. Some include different types of desensitization therapies, therapeutic message, acupuncture, and hypnosis. You mentioned depression. Some people are offended but a common manifestation of depression is often pain.
If you have been suffering for two years, you should seek a pain specialist. Be careful about who you see for pain management. You do not want someone who throws pills at you. A good pain doctor will be an anesthesiologist who has completed and board certified in pain management. Under no circumstance should anyone ever you a medication other than how it was intended and prescribed by the prescribing physician.