When will I start to lose weight?!

For a week now, I have been doing a very fast paced dance for around half an hour a day in order to lose weight (which I really need to lose as I am overweight, but also very unconfident in myself). I have not changed my eating habits, but they aren't bad. I mean, they aren't amazing, eating 5 fruits and veggies a day or whatever, but I do not eat much candy, drink soda, etc. So far, I have not really lost any weight. At least visibly. The only scale I have is really off-I know because I weighed myself twice in a row and got two different weights (like 5 pounds apart), and it's never close to the same. When will I start to see visible weight loss? I am not naturally skinny-I guess I would say I am naturally a little overweight. Will I ever be able to have a flat stomach, and keep it that way? Also, are there any other exercises I can do (keep in mind it is winter and I can't drive yet) to help me lose weight?