I've been on gabapentin for years and never experienced any type of weight gain or edema. I don't take any of the others that you do.

But, I have to ask . . .Is is just your girls that are bigger? Did you gain weight in other areas as well? And, I don't know your age but it could be hormonal as well and not MS or medications. If your girls are the only thing that are bigger, than I would venture to guess it is definitely hormonal. That does happen to many women as they age and get closer to menopause. Kind of like when they get bigger during pregnancy - and mine did. I went from my itty bitty 32A to 38DDD while pregnant. Just something to consider.