Thanks for all the replies!
He is acting alright now, and I am going to feed him in a few minutes. We just got back from being away, so I was a few days late.
He has a light on one side and a cooler area on the other side, so I turned it on at night instead of keeping it off like normal. A vet I called said to try that.
Thanks for your input. It felt to me like he ate a piece of bark or something and was squeezing it out. I'll be more diligent in the future about that! I am learning and not perfect at this, but he's well kept
He's 4 and this is the first I've seen anything like this. I appreciate all your prompt replies, you've been a great help.
mattwarbuckle