I used to have problems with my one ankle - don't know what I did, but it ALWAYS hurt after I wrenched it once. I took to wearing one of those Ace ankle bandages for a loooong time afterwards and it really helped give the ankle support. There are so many tendons and muscles down there, and they are easily torn or bruised. It can take upwards of a year to heal certain torn tendons and such.

As always, its definately best to go to the doctor. If thats not possible, buy one of those Ace bandages. You'll get flak from your family for being melodramatic, but better than than constantly hurting your ankle!