PN typically involves some damage or disease process that affects the peripheral nerves. They actually become damaged, and start sending faulty signals the brain interprets as pain.

With time, certain pain tracts become sensitized to these signals and a central pain condition may result. Phantom limb pain after an amputation, is an example of central pain.

The pain loop in the brain is pretty complex and involves several areas, and this loop is being studied quite a bit now. It involves serotonin signaling and that is one reason certain antidepressants are tried to suppress this loop.
This Medscape article explains it, but it is complex and you might have to read it several times to get a good feel for the content.
http://www.medscape.com/viewarticle/568704_9
You can join medscape for free if you don't have an ID there already.

Central pain can occur in MS:
http://www.ncbi.nlm.nih.gov/pubmed/16139182

An interesting poster came on TN forum the other day with this link:
http://www.franksherwood.com/
This gentleman claims that some peripheral pain of Trigeminal Neuralgia, can be blocked by reducing consumption of Saturated fats in the diet. It is not unlike the Swank diet for MS, but it is slightly different. Since removing saturated fat (and some of the other triggers listed) does not involve drugs, it is worth trying IMO. It is also more healthy for your cardiovascular system. How this works, remains unexplained so far, but I am including it here because it may offer you some relief.

For PN some peripheral remedies may help. We use menthol to cool burning, and Lidoderm patches for some peripheral pain.
I also use very strong magnets to block some pain.
http://neurotalk.psychcentral.com/sh...light=Lidoderm
http://neurotalk.psychcentral.com/sh...hlight=magnets

These two strong peripheral blockers may interrupt pain signals before they get to the spinal cord, and give some relief. But for central pain, they are not going to work.

Also some autohypnosis and relaxation techniques can help people not focus on pain perceptions and are worth a try. This of course is a way to intercept the pain loop in the brain. I use them frequently and have done so for many years. I credit this technique for allowing me to be RX drug free essentially for my arthritic pain and PN. (I occasionally use Tylenol or Aleve liquigels, or a tramadol at night-- I rotate use so as not to get side effects or tolerance).

Some supplements are useful. Anti-inflammatory antioxidants can help with peripheral pain, and B6 and magnesium help with muscle cramping which may lead to pain. Fish oil also helps some people.

If you have diabetic peripheral neuropathy, there are other supplements to try for that.
Benfotiamine
acetyl carnitine
lipoic acid
CoQ-10

These help some people by supporting the mitochondria which may be damaged.

Here are my supplement and drug induced PN threads.
(they are still in process, but you can get some good info from them so far:
http://neurotalk.psychcentral.com/thread121683.html

http://neurotalk.psychcentral.com/thread122889.html

It is possible some drug treatment you received in the past (like Cipro or Levaquin which are very common) has damaged your nerves --it is possible to have more than one thing going on, you know.