No need to worry, sounds like your pup has seperation anxiety, which is one of the biggest problems that a lot of dogs suffer from today. Unfortunately, it's also one of the hardest habits to break, because the idea for your dog to overcome this, is that he needs to learn that time away from mummy and/or daddy is okay. The reason why this is hard, is because the dogs that suffer from this are owned by the most caring and doting people in the world who always want to be with their dog!

So, it's something that won't be easy for the both of you.

It happens because dogs don't have the ability to tell the time (although their biological clocks know exactly when they should be having a walk or when they should be fed!), so when you leave, the dog gets anxious because he/she doesn't think you are coming back. If you come home every night at 6pm, the dog won't think "hmm, ok, it's 4:30pm now, they should be back in an hour and a half", so the idea is to basically teach the dog that being away from you isn't a bad thing.

Louise's method above works pretty well I find, get settled down (on the sofa with your dog next to you or however you guys relax), then just stand up and walk out the door closing it behind you. Go upstairs or outside for 15 minutes or so, wait until the pup stops barking, walk into the room and just sit back down on your sofa like nothing happened. Don't make any eye contact with the pup or any sort of noise.

Do this a few times, trying to increase the time spent away from your pup, only returning when your pup stops whinging. Try not to sit outside the door either because he can smell you and he can hear you

The biggest task here is feeling guilty as you leave, which results in owners picking the puppy up or just saying goodbye generally fussing over him as you leave, this only further increases the seperation anxiety upon the dog.

The thought behind it is that you come and go when you please, you are not forever attached to the dog and the dog has to understand that you as his leader, are granted the right to come and go and he just has to deal with it, which he eventually will.

On a side note, I recommend ALL owners to do this, a do with seperation anxiety can lead to a lot of problems. It can lead to soiling your house, destroying your house and it causes a lot of stress on your dog when you do leave which can lead to so many different problems down the line that you can find in dogs that lack self-confidence. Its definitely something that will make you and the dog happier.