Fell hard on my ankle, was bruised and swollen badly for weeks. Three months later, ankle still swollen and a little sore, why? Wasn't sprained.

Consult your doctor. It is common for one to experience swelling and pain for several months following an ankle injury. Consult your physician to see what treatment options are best for you.
Injury. Why not go checked by your doctor? Injury can destruct the lymphatic flow, and the swollen can last long time.