Do you work out as that will help you build muscle,also eat protein, there are protein foods out there ,supplements..is your appetite okay do you feel you eat enough, perhaps if your parents are slim it is hereditary.Dont concern your self with the meanies who tease you about your weight, it is your personality people will want to know so cultivate being a listener ,interested in others and a sense of humor, girls love a guy who can make them Laugh..
Just check with your doctor about working out with weights - many times, intense weight workouts can supress growth height-wise.
And remember, you are still within the healthy weight range - I wish I had your problem:)
Especially with 2/3 of adult population having extra weight problems....I would not be worried:)