Okay so my rat has something wrong with it her symptoms are...?

She can move she just lays on her side she isn't to old or anything only about 3 and she is bleeding out of her rectum she won't eat either but she will drink when i hold the water bottle to her mouth it's so sad this all started happening Sunday now it's Tuesday I hate to see her suffering I just wanna know what's wrong with her. Please just tell me what is wrong with her or what I can do to help her if there is anything I can do.