I have an 8 yr old cocker spaniel. She was behaving normally last night...running, barking, standing on her hind legs to try and pull garbage out of trash. We go for a 1-1.5 mile walk every day and she is not overweight. Later last night, she became more lethargic and spending time in her crate which is unusual for her. We called her to the couch and she could not jump up. My son went to pick her up to help her on the couch and she screamed. I am not sure what is wrong. She is walking normally but appears somewhat lethargic but is eating/drinking normally. I have been carrying her up/down stairs and to go potty outside. initially, when she was outside. she just looked at me. After food, I carried her outside and she went to bathroom. She has had muscle strain before, but never reacted this way. Normally, I just let her rest for a week and she returns to normal. Her behavior has never changed like this. I tried to get a vet appt. but they are booked. Help! I have no idea if this is a muscle strain or something more serious.