Sorry to hear that you are having such a rough time. Have you read the threads at the top of the page about things to do when you are feeling this way. Also, I have never been in a treatment program but does calling necessarily mean that you will be hospitalized again? I imagine that it is pretty common for people to leave and feel the way you are and that they are trained for these types of calls. You were in a "safe" place for 2 weeks and now you are out on your own. I'm sure it is pretty natural to feel that way. I have a good friend who went through an intensive eating disorder program for bulimia and the days before she left she felt pretty good about maintaining. Within like 36 hours of getting home those urges were there and she did call someone to talk about it. There is a difference between wanting to cut and cutting.
Calling them might be a great step in letting them and yourself know that you are in the process of changing your behavior. Right now you have a choice, don't wait until it's too late and that choice is taken away from you b/c you caused yourself harm.

Keep us posted...