Puppy has been fearful her entire life

I have a 4.5 month old golden retriever. Since we got her she was scared of walks as she saw and heard new things which was understandable. I started giving her treats when she experienced new things on the walks but even now at 4.5 months she gets scared of a car backing out of a driveway or a dog barking VERY far away. While I do still give her treats during these times she gets into a panic state where she pulls like crazy to go back home. When I’m holding the leash her front paws go up in the air and she tries to use her back legs to run. Any help is appreciated.