@Tamra11 - Hello, rather late to the party here, I know, but I've been going through old posts. I'm just curious if you went onto anything in place of the Gabapentin?
I ask, because I had been taking Gabapentin for my fibromyalgia. Upon seeing a neurologist for an unrelated issue, she suggested that I try Topiramate instead. Rather than weight gain it has the side effect of weight LOSS. If you take metformin, it also has the potential to raise the concentration of metformin in your system (it affects how much your body clears) and lower blood sugar in the process.
I lost 10 pounds within a couple of weeks of changing and had to drop my insulin doses significantly.
One of the unfortunate side effects though is that some foods taste weird for a little while, particularly sweets, so maybe that's not a bad thing really. Sodas can taste flat if you don't drink them with a straw. I found that those particular side effects lessened over time.