Why haven't I lost any weight?

When I went off to college, I gained a lot of weight. I am now 174 and 5'2. I want to get down to the weight I was before freshman year which was approximately 130 pounds. For the past week, I've limited myself to 1,000-1,200 calories a day and exercised at the gym everyday. I burn about 300 calories doing cardio then lift weights for 45 minutes. I also go on a half hour walk uphill every morning. I drink 16 cups of water. My scale shows I haven't lost any weight in the last week, it just fluctuates a little. Why is this? Will my diet plan eventually work? I'm a girl, by the way.
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I don't really eat unhealthy food. My breakfast is usually green tea, and greek yogurt with blueberries. I usually have almonds as a snack then either a granola bar or a slice of wheat bread with organic peanut butter. For dinner I have salad with quinao, kale, tomatoes, onions, and balsamic vinaigrette. I sometimes snack on a banana or apple. I do not drink soda, just once homemade juice.
This is how I used to eat before college and it kept me at a healthier weight, just to clarify.
Why haven't I lost any weight?
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