Do you think im to small for my age?

Im 4'10 in height, weight 90 pounds, 32A bra size, i fit in like size X-Small and Small shirts, shoe size is a 5 or 3 in kids, my jeans are a size 0, Im 15 years old yet people think im younger... Is this okay? I try to gain weight and i ALWAYS seem to weight the same, 90, ive weight the same for like two years... What can i do? All my doctor said was that mommy and daddy are not so tall and so will i be... but that he thought small girls are cute.. Blahh. I wish i had long legs and bigger breast, fit in size 3 jeans and wear medium size shirts... Any advice please?