Is my gerbil dying?please help me?

My gerbil has been sleeping non stop for the last few days. She usually is very energetic and runs on her wheel but she hasn't touched her wheel in a while. The only time she gets out of her nest is to eat, drink, or go to the bathroom. I took her out of her cage for some exercise today thinking maybe that would help her. She hobbled around for a few minutes then fell asleep in a jar filled with fabric I left out for her. Her fur is kinda fluffed up and her eyesarent bright like usual. Is she dying? If so, how can I keep her comfortable? She is around 3