Antidepressants work on the mechanisms of central pain, which may be where some or most of your pain resides.

Diazepam works on GABA receptors, and also has some antiseizure properties. Antiseizure drugs may help with nerve pain. Here is an explanation of how this works...

first post on neurons:
http://neurotalk.psychcentral.com/post828704-7.html

second post with details on antiseizure drugs:
http://neurotalk.psychcentral.com/post829772-9.html

third post with details on Neurontin/Lyrica:
http://neurotalk.psychcentral.com/post829091-8.html

Some of the posters here have found that in the beginning, the benzos like diazepam work well, but slowly this effect fades, and then you become habituated to them instead. Getting off of them then becomes a very difficult thing, with slow tapers, that can last weeks to months.

Here is an article on GABA and pain. You can copy it and give to your doctor.
http://www.ncbi.nlm.nih.gov/pubmed/17175808

If you decide to use diazepam, I'd suggest medication holidays, or sporadic use. A day here or there, for very bad days. This will reduce the tolerance feature. What happens with drugs that affect neurotransmitters, is that they over time affect the receptors, and then the body tends to make MORE receptors and then the drug stops working as before and the patients then need a dose increase.

Also depending on your age, taking Benzos like diazepam, are metabolically difficult to clear, and pose problems for the elderly...build up in the system, which causes many other problems. The cut off here is around 55 or 60, unless you have decreased kidney functions earlier in life.