I apologize for my first comment, since you are at this point where you are, but in case anyone else is reading: anyone who lets their puppies go at 4-5 weeks of age is a backyard breeder, likely with genetic issues, including mental issues, with their dogs. Shame on them!!! Never get a puppy from such a place!
Okay, now back to you. I think you really need the expert's advice here. I think you have a high strung dog and you have no idea how to bond with it, alleviate its fears or train it. Therefore, in my humble opinion, you should sit down with your budget and see what kind of training program you can commit to, involving a professional. It's part the dog, it's part you. Like llombardo said, it is possible to have a great dog, and yes, I will add that right now is a normal fear stage for your pup, but this is not a good foundation to continue and I'm glad you reached out.
I truly hope you find the help you need. It IS early, but boy, that behavior sounds not so good in the hands of an inexperienced owner. Yikes.