Eat between 1000-1200cal a day and drink tons of water, with fast pace treadmill 6days a wk...& I gained 2lbs in a wk! Why?!?!

Please Clarify. This could be that you are eating too many carbohydrate calories or sugars. Or that you are eating so little that you have turned off the metabolism mechanism in your body. Your diet, while low calorie, must contain foods that are mostly protein calories for you to have success at this. You also need to eat or graze throughout the day to keep your metabolism turned on.