What could be wrong with my ankle?

A few months ago my trainer at the gym pointed out that my ankle looked a little wonky, but it wasn't giving me any sort of trouble.. it just made my foot turn out to the side.

I hurt it a few weeks ago at badminton. I didn't feel it when it first happened but it sort of slowly came on over a few days. I saw my trainer who said it was either sprained or possibly a torn ligament, but i somehow sprained it on the INSIDE which is apparently unusual. I don't think I tore anything because it didn't hurt all that bad - I could still walk on it, albeit painfully.

Walking normally was ok, a little painful but not bad, but anything like stairs or slopes killed. For the next few weeks, some days it really hurt right from when I woke up, some days I didn't even feel it, some days it was fine in the morning and killed later in the day... very random. I was still walking on it at least an hour a day without crutches because transportation strike in my city and no money for cabs - and I never got to see the trainer again because she was unavailable.

Even though it was like 6 weeks, it still hurts at random - some days I can run on it fine and others (though only once a week or so) I wake up not even being able to walk on it. Also, when I feel the back of my ankle, it feels sort of "creaky".. It's not a smooth movement and I'd explain it as the same feeling as the friction of your shoelaces getting done up, or the feeling of doing up a zipper. The normal one feels totally smooth when I move it.

What could be wrong?