What Causes Severe Upper Ankle Sprain And Pain?

Woke up yesterday morning with what feels like a bad upper ankle sprang. I did nothing different then I usually do. It bad pain both sides of my ankle and come up the back of leg at times . Since I did nothing to cause this it's very confusing and don't have money to go to a Dr only to an er and make payments. If there anything that can cause this without injury? I'm a 38 yo male. Thanks