Quite often many are too quick to think that their dog has separation anxiety simply because there may be a few problems when the dog is left alone. True separation anxiety quite often has some underlying medical condition which should be assessed by veterinarians. Once the medical problem is adressed then the behaviors can be fixed. Also many times an owner may come home to a disaster at home and may decide that the pooch has a problem with being alone when in truth the dog is just releasing some pent up energy. True separation anxiety manifest itself in most if not all the following forms: whinning, barking, self mutilation, destructive behavior, excessive salivation, and having accidents (sometimes to the point of dehydration). If the dog doesn't do this within the first few minutes of your departure (you can use a camera to find out), isn't by your side (a velcro dog) at all times when you are home, and isn't able to sleep unless he is with you; then the most likely thing is that the pooch is either bored when you leave or simply hasn't been conditioned to being left alone (minor confidence problems). If you suspect true separation anxiety contact your vet as soon as possible and fix any medical problem if there happens to be one, if the dog is healthy then continue with behavior modifications, plenty of exercise, and some confidence building exercises. The following information deals mostly with mild cases of what might be called separation anxiety but can also be used for dogs that simply lack confidence in themselves.
Separation Anxiety - dog separation anxiety, barking when left alone, Lack of confidence
I think that the first member nailed it, this seems like a pup that needs to go out more and lets face it, simply is being a puppy! The two things that are most likely going to help this problem get better are two things 1. Exercise (no, not a 5 minute walk around the corner, I mean a 30-60 min jog/walk, or a couple mile walk). Fetch is also a good alternative. 2. Obedience training. Have you set down rules in the house and constantly enforced them? This along with basic obedience exercises mentally stimulates a dog and allows them to figure out what they can and cannot do while left unattended in the house.