How come I cant lose anymore weight?

Im 17 years old, I have a medium frame and am 5 feet 5 inches tall. I used to weigh 217 but did Atkins Induction for 2 months sticking to about 15 carbs a day. I run a mile every day and do weighttraining. I cant seem to get below 189 no matter how hard I try. Can someon give me suggestions on how to lose more weight i want to get down to 160. Thanx