Using the information below, would you say I'm fat?

I'm 15 years old, and I will be 16 on the 8th of August. Whereas most of my other female friends are tiny little things mostly between 6 and 9 stone, I usually hover at 12 stone. I am quite short - I was 5 feet, 5 inches the last time I checked. I have started going swimming every day, but it doesn't seem to affect my weight. My daily calorie intake is about 1500 - 1800 calories. With all this information in mind, would you say I'm fat?