German shepherd behavior + food

Question
I have a 3 month old pure German shepherd, and he's really shy/scared
when it comes to any loud noises indoors and outside.  We just got him
about 2weeks ago and he seemed fined then; I mean he would
walk with his head held high, and he was the most active of his litter.  
Yet I don't know if this is what it was, but I feel that my German
shepherd has been different ever since my neighbor's old lab mix, all of a
sudden, ran up to him barking in my back yard, (my puppy was 11 weeks
old at that time). Now he seems to afraid of
vacuums, cars, other dogs that bark at him, and doesn't like greeting people too often, but at times hes completely fine with people.
He seems to be completely different, and seems to scared to go for
walks thou.
Also I have another problem, even since my puppy came back from his first day at the puppy training class he doesn't eat properly.  He would only eat a little of his food, but if we took that same food in our hand about an hour later he is able to finish it all up. Is this behavior normal?
Any help would be great.
Thanks


Answer
It could be that your pup is going through a fear period, Serena. The important thing is that you must NOT react when he shows fear. Just ignore it, completely. If YOU are confident, that will rub off on him and he will become more confident. Do not force him to accept people petting him, and do not let other dogs approach him. If you're walking him and he balks at something, like a loud car or skateboarders up ahead, try stopping your walk (do not give in and let him pull you away from whatever it is he's afraid of, though) until he's stopped trying to pull away (you may want to consider a martingale style collar so he can't pull out of it). Then, tell him to come on in a cheery voice and continue.

At the puppy training class, are you using treats or food? That could be why his appetite seems to have diminished.