new gecko question

so i have a fun new gecko question, my jumbo leo is hanging out on the cold side alot and sleeping night and day. i can NOT figure out why. his heat pad is good humidity is good. not eating very much but still at a healthy weight. any ideas whats going on with him?

What are the temps? They don't need "humidity" really, a humid hide is usually fine. What is the substrate, any chance of impaction? How much is he eating and is he pooping?
Have you tried offering different feeders (what does he usually eat?), sometimes something different will be all it takes.
Sometimes they just do this too...but it is, in my experience anyway, usually the females that go on little hunger strikes. I have one girl who has just started her yearly nonsense, she won't eat for a long while and will lay a few eggs then go back to normal.
As long as there is nothing wrong, his cage is good and he's not losing weight a bit of not eating should be OK. Obviously you need to keep a close eye on him though...