Hi, I'm sorry you're going through this! It sounds like we're kind of in the same boat. Now, imagine this: I'm under 16, 5'1"-5'2", and normally 105 pounds. In THREE WEEKS from being on Neurontin I gained almost 15 pounds! That's a lot for someone as small as I am! I also go NO pain relief. I'm now trying Topamax, another anti-seizure, which commonly makes people LOSE weight, and it's very effective for headaches especially. I, however, have brachial plexus and cervical plexus neuralgia, so I don't know how it will help me, but I'm staying optomistic, and I'm going to look forward to this weight finally coming off.
Perhaps you could ask your doctor about Topamax??? Good luck and I hope you feel better soon! I don't know if you're religious or not, but I'll pray for you.