I agree with everyone else ... the BMI chart shows you are already at a healthy weight. If you feel you're not, you can exercise your way to perfection. And I couldn't agree more about not worrying about models in magazines ... either they are air-brushed or they at unhealthy weights. Whatever anyone ever tells you, achieving and maintaining a healthy body is what is attractive and it is always in style.
But the good news, IMO, is that the trend seems to be going back to larger, more fit bodies, rather than everybody having to struggle to be sizes that are not normal for them. Some people are thinner than other people, some people are larger than other people. You are at a size that is just right for you. If people tell you not to eat because THEY are uncomfortable with their weight or whatever, those are just lies. They tell those lies because they don't know any better, but you do. You know you are perfectly shaped and healthy and no one should ever be able to tell you otherwise.
Although I know she is hugely older than you, look at Christie Brinkley. In her life, she's become one of the most successful supermodels ever, yet people used to say she was too "big."
I hope I look just like her when I grow up!