I'm not considered plus size am i?

My sister, who is plus sized for sure, always tells me i'm a plus sized teen. But, i'm confused. I wear size large shirts in juniors, size 11/13 pants. I weight 157, and i'm 5'2. But i'm not really fat, or obese. I have extra weight, but it's in places like my thighs, and arms. My stomach isn't THAT big, I have a belly but not huge. Am I plus sized??