WHAT IS WRONG WITH MY DOG PLZ ANSWER I'M SCARED?

Ok so yesterday at about 6ish she started randomly whimpering for some unknown reason. She usually doesn't bark at all, so this was a surprise. We couldn't find anything that she might of eaten and no one was around her when this happened. Later, at about 9ish, I was petting her. I accidentally leaned on her a bit and she whimpered again. At this time, she seemed resistant to moving, staying in the same spot where I had upset her when she would normally move somewhere else. At 12ish today, I find her sleeping on the floor next to her bed where we had put her that night. Usually when she gets hot she goes upstairs and sleeps on the bathroom floor, but she was too weak do that. Also, I tested her with a treat. I krinkled a bag crinkleditchen and called her name, to which she'd normally come in looking for her treat. But, she stayed in the closet, wagging her tail. What is wrong with her????? Please help me I love my dog and I would be devastated if adivested happened to her. She is a four year old Cavalier King Charles Spaniel girl. We live in Chicago suburbs and it was pretty hot yesterday. IDK to say... PLEASE HELP!!