--that's a tall order, I'm afraid: A neuropathic pain medication that will not cause weight gain, has little effect on the liver, not cause irritability or sleeplessness--and will be effective.

Welcome to the boards, by the way--and please come over to our peripheral neuropathy section (very active and lots of knowledgable and empathetic personalitites):

http://neurotalk.psychcentral.com/forumdisplay.php?f=20

The med that comes to mind is Topomax, another anti-convulsant (same class as gabapentin/Neurontin and pregabalin/Lyrica) that many have reported weight loss on, as it seems to curb carb cravings. But, it's not without its own side effects (chief among them a greater tendency to develop glaucoma--not something you probably need as a diabetic). And, not everyone who has tried it has had success; some have even reported symptom upticks (of course, this can be said for any medication used for neuropathy--we're all experiments of one).

You've mentioned not having had a good time with Cymbalta--I wonder if another of the older anti-depressant/neurotransmitter regulators might be worth a shot for you (such as Elavil), but these also tend to be hard on the liver . . .

Perhaps an attempt to find some non-pharmaceutical agents? Many with diabetic neuropathy have had good results with alpha lipoic acid or R-lipoic acid. It's sold as a dietary supplement in the US, but is actually considered a prescription substance in many parts of Europe, especially Germany, where it has been a mainstay substance for diabetic neuropathy for decades.

There are also the possibilities of Anodyne/infrared therapy or the Rebuilder device (which is sort of like an advanced TENS unti combined with an ionic foot bath).

I'm sure you'll get other suggestions over at the neuropathy board.