Yeevo

I have a boy black lab (Clyde), He's around 2 years old. I dated a girl, and broke up, but she wanted a good home for her dog, cause she couldn't keep him anymore. And she had Frontline for him, All his shots, she gave me his papers, shot records everything. But this is the problem.. If it's me and my dad home. He's a perfect dog, Housebroken, NEVER goes inside unless he's been in ALL day. Doesn't snap at my cat. He listens, basic commands. BUT, When I sit him by the door.. Put his leash on him. Tell him let's go outside. He gets SUPER excited. But as soon as I open the door, he stops. smells, looks around his surroundings. Then stays there, if anyone even a 3 year old girl walks by he gets scared and runs inside. The slightest noises make him scared. Even if he's laying in bed with me, if a pillow falls off, he gets uncomfortable for about 30 seconds til he realizes it's nothing. When I take him around other dogs, he's fine unless they try and do something too him. I put him in my bed of my truck, with a harness and all, take him on the freeway. he doesn't freak out at all? it's very wierd. I'm so frustrated. I just need some help. I love Clyde. But i'm almost at my end...