It’s not about how much you weigh at what age, really, it’s about your lifestyle and body type. It sounds like you’re living a pretty healthy lifestyle, keep eating well and exercising since your body is still developing; you’re doing a great job. Remember, people with different body types require different weights, so depending on yours, you could be right where you need to be. Taller people have to weigh in a bit heavier, generally, and people on sports teams are sometimes required to keep a certain weight. Continue your good work, you’re doing just fine!