First off a couple questions.....
In the past when you have tried to lose weight has your family been supportive? Kept good healthy foods in the house for you to eat/snack on (fresh fruits, veggies)?
Do you eat a pretty healthy diet now or is it full of sugars and snacks?
When you exercised did you start out going full force or work up to it?
I'm guessing because you dont see immediate results is why you have given up after just a few days?
Unfortunately the weight didnt go on overnight and it wont come off overnight...as I continually tell myself.
Finding a support base (like this web site) is a good starting place, and if your parents are supportive of your efforts to lose weight have a heart to heart with them about how they can help you be successful...mainly in the food dept and encouragement.
Things you have control over (for the most part) is what and how much goes into your mouth
Start slow and replace salty high fat and calorie snacks with healthy alternative...carrots or even some of the pre-packaged chips (Special K makes a cracker-chip that sells in bags only 90 calories). With exercise the key is just get out there an move...walking is a great start and you can walk slow or as fast as you are comfortable. Slowly increase distance and speed. A pedomitor is great to show you how much you actually do walk. Many times people think they are doing way more than they actually are.
If you are a data freak like me, track your calories normally for a couple days to see exactly how much you are eating, then determine you BPR (I think it's called...the minimum you need just to stay alive) That can give you a good idea of how much you should start cutting back. And then start slow.
If you are used to eating say 3000 calories a day and drop to 1200 and add exercise your body gets rebelous LOL you will be fighting hunger, and if not used to exercise possibly sore muscles... start small and say I'm gonna only eat 2500 and walk 1 mile today (or 3000 steps). As you adjust to the lower calories and the increased activity...drop cals or up activity or a little of both.
Also make little mini targets along the way...say after losing the 1st 10 lbs do something fun...or get nails done, or a special treat....
You want to loose the weight and YOU CAN!! Don't beat yourself up for the little hiccups along the way