Please help!

I have a fancy bear Syrian hamster I'm not sure of her age we brought her from pets smart. Its been a couple of months having her. This morning around 4 something I noticed she wasn't dugged up in her bedding. That's how she sleeps. When I looked at her she looked like she wasn't breathing I moved the cage and she didn't look alert like always. She was just laying there not moving. She was only able to move her back and front legs a little. It looks like she tried to pick her head up but couldn't she looks weak. My husband picked her up but nothing just layed there. She's breathing but not moving around, opening her eyes or doing anything. Her back part of her body looks weird like it is sunk in a little. What's wrong with her? I just had my cousin pass away on the 20 th I can't have her die on me to. Please help!!