Ankle hurts!

I am 14 yrs old. I sprained my ankle 2 years ago and went to the doctor. He knew it needed the attention of an orthopedic surgeon so I went to one. After x-rays, he concludd it was just a bad sprain and I wore an aircast for a while. It felt like it healed after 3 weeks, but after a couple of days without the aircast it hurt again. I have gone back to several differt doctors since and they say nothing is wrong. I am very frustrated. What should I do?