Dog all of the sudden wont walk on leash and scared to be outside

Question
My question is about my 1 year old dachshund. My girlfriend recently moved out along with her dachshund. They had been together since November 09, when I adopted him, and he's never had a problem walking on a leash, or going outside. Ever since she left 4 days ago, he won't go out, and when he is out, he will barely go to the bathroom before wanting to run back in. He is acting scared. I stand out there with him the whole time, but have to carry him out.
As far as walking, he will not go willingly, and just sits down most of the time. I got him to walk yesterday and today after some work of trying to get him to move forward. Once he's going, its fine, but, its hard to just get him to go. He gets excited when I tell him we are going for a walk, but won't even come out of the door now. When he is out, he's very timid now, like something is going to get him. Every little noise seems to startle him.
Any advice to help him overcome this would be greatly appreciated.
I should add that he is fine inside. Playful and full of energy.
thank you.

Answer
You should first understand that a dogs behavior is heavily controlled by its environment.  Your dog's environment has changed dramatically because of your roommate's leaving.  From the sounds of it your dog had placed both your roommate and her dog in a leadership position and now that the leadership is gone it doesn't know how to act.  This is not a time to coddle or feel sorry for your dog instead it is a time for you to step up and assume the vacant leadership roll.  It has only been 4 days and time will itself take care of the issue as long as you don't inadvertently reward the misplaced fear or behavior.   Don't spend a bunch of time trying to coax it to go outside or for walks.  The dog is small simply pick it up and take it out and then place it down when your outside the house.  Control is essential so have a well fitted collar and lead and simply insist that the dog comes along with you.  A tug and release method is best to use if it resists and doesn't go on its own.  You may even use a little reverse psychology by simply not taking it for walks for a couple days.  The behaviors your dog is demonstrating will only become habit if you allow them to be rewarded in some fashion.  One simple approach would be to just ignore the behaviors and go about your usual routine with the dog.  Whether it pouts or not simply continue your regular routine with little to no attention placed on the undesirable behaviors.  I would also suggest that you begin a regular training program to get and maintain control of your dog.  This program will also help environmentally socialize the dog so that it will be less fearful of change within that environment.  You should be able to expect a certain level of participation from your dog.  If you do not then the dog will certainly be happy to live up to your lack of expectation.  I would suggest that you purchase my ONE, TWO, GOOD DOG! booklet.  It provides your with the basics of control and obedience with your dog.  It does so in a simple straightforward protocol that anyone can understand and use.  It focuses on a 5 minute time frame for most learning and uses integration to build a closer bond and relationship with your dog.  (http://invincibleservices.com/html/one__two_good_dog_.html)  this is the web page.  If after following my direction you do not see the behaviors changing in a couple weeks please call me.  Dr. Hogan  509-991-0385 until 10:00pm pacific.