My puppy is acting really bizarre. It really has me worried.?

We just got a 4 month old Border Collie/Aussie Sheppard. She's not acting anything like we expected. Because of the breed we were expecting a hyper dog that we were going to have our hands full with but she is acting bizarre. She drooled excessively in the car ride on the way home, and she didn't investigate the house at all. She just laid on the floor and didn't move. She refuses to go outside, and she also won't walk. To get her outside, I have to pick her up and carry her out and even then she just sits on the ground outside and doesn't move. She's eating and drinking (although not a lot) and she is having bowel movements. She also will not walk on the leash. I have tried coaxing her, and I have also tried umbilical. She simply lays down and will not move. She will actually go as far as making me drag her until she starts to choke. I'm worried she is depressed or there is something seriously wrong. She is not acting like her breed at all. Any ideas?