What's the water temperature? Do you have it heated for him?
Is he in an aquarium that's indoors?
Is he moving around some of the time?
You don't want him to be in a semi-hibernation state, it needs to be all or nothing with hibernation or else it can lead to illness.
If he hasn't eaten in this long, if he were mine I'd take him to a reptile vet.
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PHRatz