I was overweight all my life. At your age I was probably 100 pounds overweight, too. Despite some temporary drops, over time I gained more and more until at 39 I was double the weight I should be. Now, 3-1/2 years later, I'm within about 15 pounds of my final goal, the least I've weighed since about the 4th grade. Trust me, I know all about the embarrassment, the misery, the despair. I've spent large portions of my life right there, and before I started my current program I was so mortified I could barely move. But, I was determined to live the last half of my life as a normal person. Face it, I was determined to HAVE a last half of my life instead of dying young.
I won't lie and tell you this is easy, or fast. But, it is so worth it I cannot even begin to tell you the benefits you will reap. And, once you make up your mind to do it, it's like there's no holding you back. Sometimes you start the process and trudge along before that mindset really clicks in. It WILL, though, if you encourage it and nurture it. If you take every step of the way grudgingly, mourning your old food habits and the protection food and a fat body gave you, then you won't make it. But, if you take one day at a time and focus on the positive, then before long you'll find that this is just an integral part of your life, challenges and all.
The first thing I would recommend is going to the library and checking out the book
Thin for Life. This is not a diet book but has a series of "lessons" learned from people who have lost a significant amount of weight and taken it off. In fact, the maintainers' group here on 3FC has a discussion group going about this book in their library section. This book will help you start to think about this process and maintenance in a positive way, offer practical advice, and also give you some very good "success stories" and role models. Also, if you think you may be a compulsive overeater, I highly recommend the book called
The Thin Books. It was a real eye-opener for me about how my thought patterns and impulses were behind my overeating.
Second, start reading the maintainers' forum here, expecially the "stickies." There is a wealth of information there about what losing & maintaining are all about.
Third, you HAVE to start talking to yourself in a positive way, EVEN IF YOU DON'T BELIEVE IT RIGHT NOW. Here's the thing -- You believe what you hear if you hear it often enough. Your post is filled with negative self-talk: Self-hatred, believing that you can't lose, setting up impossible goals (you not only want to lose, but you want to lose quickly), etc. One of the things that Thin for Life talks about is positive self-talk. Even if you don't think it's true, STOP telling yourself you can't and START telling yourself you can. If it helps, don't think about losing 100 pounds, think about losing 10 pounds as the others suggested. I haven't lost 165 pounds -- I lost 10 pounds, then 15 more, then I got to 299, then to 280, etc. Set whatever goal you think is doable, and keep telling yourself it's doable. Then, when you reach it, you will feel validated and a wee bit more confident, and you can let that feeling of success fuel your next goal.
The other thing I want to mention is that it really helped me to stop thinking about "dieting" and "losing weight" and start thinking about permanent lifestyle changes. I realized that whatever I did would have to be something I could live with the rest of my days. I had to think of my obesity as a disease that had to be managed. I wanted to turn around my eating habits not just to lose weight but to have a healthier body. I wanted to change my use of food as a drug for the sake of my overall mental health, not just to lose weight. I wanted to be more active because being active is GOOD for me, not just to burn more calories. It's not about doing things you loathe to become slim -- it's about developing a healthier mindset which allows you to enjoy healthy food and activity, the BYPRODUCT of which is a thinner body.
I know you are scared and apprehensive and you feel trapped. Trapped by the fat, imprisoned by desire for food, and paralyzed by the idea of the amount of work and mental effort this is going to take. As you've seen, that's perfectly normal. After all, in a way you will be turning your life upside down in order to get where you want to go, and sometimes that seems too daunting. You'll be stepping outside of your comfort zone daily, hourly. Then, if you do get there, then what? What will life as a thin person be? What if it doesn't solve all my problems? Etc. Yes it's all very scary. But, it's also a grand adventure. Always remember that if you're being pushed out of your comfort zone -- by going for a walk, or turning down dessert, or finding some other way to cope with emotion besides a drive-through -- you're building a better, stronger you. You're building a person who is not only healthy physically, but mentally. Your body will start to thrive rather than exist. It will become more than just a shell to carry your brain around, it will become a source of enjoyment all on its own. You'll start to live as a full person again, rather than a person trapped inside a protective, alienating coating of fat.
You can do this, I know you can. I am very proud of you for trying to come to terms with this so early in life, and for coming here for help. Just try to remember, one pound at a time, one day at a time, one bite at a time. You won't be perfect, you'll make plenty of mistakes. That's OK. As long as you keep that long-term view and keep putting one foot in front of the other, you'll get there. How long it takes doesn't matter, because you're going to be walking this path the rest of your life.
P.S. If you are looking for information on how to build a good eating program, I recommend
www.fitday.com. Setting up an account is free. It is primarily a web site where you can log your food and activity, but they have lots of good information on healthy eating that you can read and apply.