Weakness in leg i sprained ankle on april 2010?

last year april 2010 i was out working when i came off a step and landed down on the side of my left ankle, my foot twisted inwards, my whole leg got hot afterwards. i went to the doctor about two days later, my ankle was swollen and painful, done the rest ice compression elevation for a couple of weeks, my ankle healed up fine though it took a few months, or so i thought up until a few weeks ago when i realised the injury was still there i play basketball i got an accidental push in the basketball but it was only when i got home i noticed my ankle starting to swell up and pain me again, had to take tablets. ever since on and off i am getting sometimes stiffness in the lower back of my leg also my leg has become weak to stand on as i do feel my leg is giving away from under me i also get twinges of pain example on the top of my foot sometimes on the back of my foot around heel area and through my toes sometimes when i walk on that foot last night for example i heard and felt what was like a popping on the top of my foot. i have very flat feet which i believe can be a problem but i do wear orthotic lift supports for that. i never received physiotherapy.