I'd say it's been going on for a week and a half or two. I just weighed him, and the scale says exactly what it did when I first got him, 2.8 pounds (~1270g). I feed him nearly-full-grown rats.

Looks like he's going into shed again, which is odd with no weight gain, but he's getting the pink belly again. I'll just wait and see, and if it keeps up, to the vet he goes.

Thanks guys.