I really need your help!

[Nakuzo]

Oscar, my hammie is gradually waking up later and later. It got to the point that he know wakes up at 00:30 or later. If I get him out to free roam, he keeps trying to get back on his cage. 1 month ago he wasn't anything like that. He was practically begging me to get out and free roam, we had so much fun and he would be out for an hour or so. To give you a point of reference, he would wake up at around 8:30 pm a month ago. He is also asleep when I wake up at 7am and I am extremely worried. Please help!