Build a life that you find truly beautiful, fascinating, inspiring, and meaningful. Wake up every morning inspired by the beauty, signficance, meaning, and value of your life. When you have a reason to lose weight you will lose weight. This isn't an illogical situation, you were in control of yourself the entire time and still are. Find the reason to lose weight that satisfies you. Without a reason why should you put in the effort?
Find your purpose. Find your purpose. Find your purpose.
I really do feel for you. At 17 when I was in high school I had no reason to lose weight. I was 5'8'' 240 lbs, massively obese, big ol' man titties, tight size 42 pants, long greasy hair hung over my bloodshot eyes, my rancid breath spewed hate towards any who dared interact with me, I was the definition of sexxxy. I was mean, bored, and massively depressed. My life was a train wreck. I didn't want to be popular, I had no plans to help the world, I had no plans to do anything, I hated exercise, I loved crap food, I was depressed, I was forced to go to a school where I hated the classes, the teachers, the students, and myself. There was little reason to do much of anything, much less care about my weight enough to change it. I cared enough to yell at myself for it and use it as justification to gain more weight. I grew up in a suburb where there was nothing to do, no one was inspired, everyone was shallow, and life seemed cold, meaningless, and painful. I had no visions of being Einstein, I had no visions of mattering at all, things like weight were just playing into the game of the suburb, just playing the game of meaninglessness. Eventually I've found through self-education that there are things beyond what I have been raised with. There are humans of great value and importance. We all have the potential to be such a person. Knowing that is what inspires me to be healthy. Knowing that is my reason to get out of bed. Knowing that is why I gave up on my slow decay.
Find a purpose to give your life more meaning. The great people throughout history haven't been concerned with trivial things as a little extra adipose tissue. What does the great person inside you have to say about health? What does your Einstein, Hippocrates, Gandhi, or Jefferson have to suggest to you? If you are going to make an impact on this world we want you to keep yourself healthy and on the path to making that impact for as long as possible. If you are going to be fairly neutral or potentially destructive we want you fat, meaningless, lazy, and unimportant. Step up all of your life. Become someone important. Find your purpose.
Do we remember that Einstein had a spare tire? Do we care? Is a life devoted to the adoration of your physical beauty worth living? What happens when you age? What happens if you are in an accident, require surgery, get a disease, or get stretch marks? You are young. Even if you lose the weight and become physically beautiful in most cases it is not going to last, certainly not at the level you have now. Time is not kind to physical beauty.
Figure out why you decided to become fat. Figure out why you don't want to be fat.