I moved into a new apartment a week ago, and for a few days now, he's been sleeping with his head slanted in a 15-30 degree angle, then last night, he had his head sitting on top of his hide, while the rest of his body was inside his hide.
Then today I took him out for the first time, which he seemed okay, but when I touched his head by accident, he didn't even react to it, it was odd, so I did it a couple times, got the same response, so that is worrisome to me. However, I did do this a bit later after he was back in his tank, just to see, and this time he did respond to it.
I have a vet appointment for him in the morning, hopefully it's nothing serious.