Ankle?

I am a little confused. My ankle/foot has just started a new game where it will begin to throb with pain if I do just a little more than a few minutes of walking. I do not remember twisting, jarring or otherwise traumatizing my ankle/foot. I bought some shoe inserts (now I feel OLD) which seems to help on the short trips. Today, I guess I will see if I can handle a longer jaunt. I am just confused as to what is going on with it. I guess I will have to see a pediatrist.