~Why did I gain 6 pounds in 2 days?! I'm sticking to my diet and eating healthy!!?

So I have been eating healthy for about 2 weeks. I cut out all junk food and eat lots of fiber, veggies, and fruits. I went from 110 pounds to 103 pounds and it was going well until yesterday morning. So yesterday morning I woke up and I was 103.5 pounds. Super happy. I had a cup of soymilk for breakfast, and a piece of whole wheat bread with light cream cheese on it for lunch, along with a salad. For snack I had an apple. And then for dinner I had a small bowl of rice, tofu, and veggies. I calculated that to be about 1000 calories. Well I weigh myself at night and it says 106 pounds.. wtf! I have never gained so much in one day. Then I go to sleep without eating anything else. In the morning after I pee I weigh 107 pounds! How?! So today I had a granola bar for breakfast, a turkey sandwich and yogurt for lunch, and carrots as a snack. I come home, weigh myself, and it says 109!! I feel like crying. Where did I go wrong? Do you think it is a problem with my scale?!!