Oh, man. I'm almost 25 now, but when I was 15-18, I was also always eager to lose more weight to be thin. I am small-framed and 5'2" and gained 60 pounds at age 18 due to antidepressants, but before that, I was 115-120 lbs. and I ALWAYS wanted to be thinner. I thought being below 110 would make my life perfect. Now I can't imagine why I was distraught to be 120 lbs. It's a healthy weight for someone our height and frame-size.
The weight range that FitDay has given me is this:
The healthy weight range for your height is between 101.1 lbs and 136.7 lbs.
So it sounds like your growing body, responding to your needs as a dancer and your increase in exercise (which may be increasing the muscle mass, NOT FAT, in your legs--muscle weighs more than fat, remember), is just trying to find a weight at which it's comfortable. I know that any weight gain may seem incredibly noticeable to you, but I can almost guarantee that no one else around you is looking at you or judging you as harshly as you judge yourself. I worry that you would want to try and drop to your prior weight--you sound like a healthy and fit young woman to me who should focus on training and strengthening your body and NOT the number on the scale! I hope that you can find it in yourself to accept those dancer's legs as a part of who you are and not a hideous deformity.
I feel like perhaps the binge eating may be a response to not getting enough calories for the growing muscles. Given that you exercise so much in a day, it's critical that you get enough calories to support development and growth and also maintain your body's normal functions. Have you tried eating several small meals a day instead, spaced out every few hours, and ensuring you have something small to eat after you work out for 3 hours? I would start there.
Good luck to you, Lea. I hope my advice helps. I can't in good conscience tell you that you should or need to lose weight--I know how it feels to want to be thinner and I now know it just isn't a healthy path to take!
"Oh, he is gone... he's my insatiable one." -- Suede.
Current Weight: 207.4 lbs. (6 December 2010)
Short-Term Goal: 188 lbs. (12 February 2011)
After That: 165 lbs. (April 2011?)
And Beyond: 140 lbs. (August 2011?)
(Very) Long-Term Goal: 125 lbs. (December 2011? Never?)