It's the gabapentin. I've been on hefty doses of gabapentin (5g or more daily) for a while now, and have noticed significant water retention. I stopped suddenly last week and it was a rough week, let me tell you. I also take kratom; however, even since just last week, I have noticed some of my water retention is gone already, in my neck, my feet, just everywhere. I got a refill of gabapentin today and, despite my vow of never again, the cravings were strong so I took 1.4g. Didn't seem to do much, but from past experience I have noticed 2g is really the barrier before I got much benefit from it. I'm vowing not to take it daily anymore, though, especially when I read that it's theorized that gabapentin may prevent new brain synapses from forming at all, and may interfere with new memory production, among other bad effects. I didn't realize people were having seizures from suddenly stopping high doses like I did, so I feel a little lucky.