One thing I've found over the years, the list of side effects on most medications not only doesn't get all of them, but it also lists a lot of side effects that never show on me. For example, nowhere on the list of side effects for Neurontin does it say anything about it being hard on teeth, but I'm here to tell you, it was hard on mine.
By the same token, I've taken medications where the side effects include all sorts of things that I never experience while I'm on the medication.
The best thing to do it change or add meds only one med at a time, and give that med several days, if not a few weeks for any side effects to show up. Sort of take stock of yourself several times a day while you're starting the new medication, and see if you feel any different. I think a month is the best time for that assessment. If you're not getting any help, or if several side effects you don't like have shown up after a month, then you probably ought to talk to your doctor about discontinuing the medication, increasing the dose or decreasing it, depending on what's going on with your body.
Cymbalta is a very mild anti-depressant, but it's very effective also, and as you say, it's also used very effectively for treating neurogenic pain.
Lots of love and healing hugs,
Dan