am i really underweight? <33 THANKS!?

i'm 15, about 5'7 or 5'6 1/2, and i usually weigh somewhere from 92 lbs. to 93 lbs. my weight fluctuates a lot. people say that i'm super super skinny and i look anorexic, but i don't see it that much. you can see the faint outlines of my ribs and i have basically no body fat anywhere but my upper thighs, which are kinda squishy yuck, and my hipbones. if i stretch up just a little bit, you can count all my ribs. i think it's just because my limbs are really long, but am i really that href='http://ellern20.vilablog.com/2011/02/12/is-it-fair-to-say-that-billy-wagners-career-has-been-as-good-as-trevor-hoffmans/'>underweight for my age and height? my waist measurement is 21.5, my chest is 28, and my hips are 31.