Replying to Strange Ankle Pain When I Run

So I play lacrosse everyday after school for like 3 hours. And the season just started like two weeks ago. Now I'm getting this pain in my ankle during practice. But not at any other time. When I start to run it hurts and continues hurting and then like a half hour later after practice whne im sitting doing nothing its better. I never really had an injury to my ankle that would cause this. It just kinda slowly started, it feels like my ankles have so much pressure on it and is just worn and tired.

Anyone know what this is or how to diagnose it?