Open Question: Help?! I’m 17 but Prescribed a Drug for over 18s?

I have held a second of my psychiatrists and social workers today. They said I was suffering from very severe anxiety, and perhaps something more, but they have not yet discovered, I have prescribed sertraline, and I will have to cognitive behavioral therapy. My psychiatrist said that I will be a small dose of sertraline, and will her on Monday, about the drug's work, and then look at me next week, they are also CBT. She told all of my possible side-effects, but later when I went to pharmacy drugs it says to do so, if you do not take under 18 years of age? But she told me that you can earliar, it is a small dose, and will be improved, and so on. Can I? I am a little worried about …