dog behavior problems

Question
I have a 4 month old Labrador retriever. He has growled and tried to attack me before, when I took something from him. This morning he tried to rip some plastic strips I have in the garden and when I said NO to him in a loud voice he growled at me and prepared to attack me. I was so scared that I just said No! again and he stopped. I am pretty sure he didn't attacked me because the plastic strips (that are hanging from the ceiling) were a kind of barrier for him at that moment. I am afraid to even take him outside. Is this behavior normal? How should I handle him now. I know he can feel that I am scared of him. Will this fear cause  him to try to attack me even more?

Answer
Yes, if you continue to be afraid of the dog, his behavior will just get worse.  It's just a simple case of the dog not respecting you.  If there is no leader in the house, the dog (even at 4 months of age) will assume the role and he's growling at YOU telling you that YOUR behavior is not cool.  

I would find a training class immediately and enroll.  Talk to the instructor about what's been happening and they should be able to help you train the dog so that you rule the home, not him.  This is best worked through with an expert who can be with you and your dog personally.  

Good Luck.