I sprained my ankle 6 months ago and it still hasnt healed why?

you could have fractured it, i did that in September so you could get it checked out but more likely it is just a sprain and sprains are pretty stupid injuries they will bother you forever. The same ankle that i fractured in September i sprained in April and it still isn't healed. Just take anti-inflammatory medicine, like Advil, and ice it to reduce swelling also if you play sports wear braces to help support and prevent further injury.