Today when I was feeding my garter I noticed he had a ton of wrinkles on his underside. They started about 1/3 down his stomach and then in some spots there are two or three wrinkles next to each other. They all flow straight down his underside. I'm pretty positive its not stuck shed since he shed less then 5 days ago. He's acting normal.

I'll try to get a photo of him pressed on the glass.
I read somewhere that it could be scale rot. Hope not. He doesnt have any excessively wet spots in his tank. Sometimes he'll splash water out of his bowl and sit under the plant on the damp paper towel, could that be it?