This is not working

I was feeling really good this weekend because I weighed myself Saturday morning and was down two pounds. Then I weighed myself this morning and I am back up the two pounds, exactly the same weight I was the morning before I went to the nutritionist for the first time. (I weighed more when she weighed me, but that was a different scale and it was during the day, when I had already eaten, and I was dressed.) So what is the fucking point of doing this? I did the best I could over the weekend. Sure, I ate in restaurants, but I didn't go crazy. I had half a chicken gyro wrap on whole wheat pita Saturday night, and on Sunday I had half a chicken shawarma pita for lunch and the other half for dinner. It's chicken -- how bad could it have been?? Also, both days this weekend I went to the gym, and really worked out hard for half an hour on the treadmill. (Which was a lot for me, but hardly enough to make the claim that I'm building muscle and that's why I'm not losing weight. Um, no. An hour total of cardio is not going to build any muscle.) So why should I do all that when I can go back to the way I was before and weigh exactly the same? This is fucking crap. It's officially been one week -- the other woman doing this lost 5 pounds in her first week, and that was without going to the gym. What the fuck is wrong with me? Why can't I do that?