Help. I don't know what is wrong with me girl.

[Gidgetgirl]

I need some helpful advice. I got my first hamster in September of 2016 at about 6 months old. Now It is March and she has started acting different. She is not active at night really anymore. And she has gained some weight over the past month. She just wants to sleep all the time. Fearing it may be hibernation do to this time of year I have a reptile heating pad under past of her cage. Eating normally, bathroom rabbits are mostly normal but is not using litter box and drinking is normal.

I just need to know if I am doing everything right???