My ankle is throbbing! What's wrong with me?!

Sounds like you may have sprained or strained your ankle somehow. Do you remember turning your foot over (rolling your ankle)? You can apply ice to relieve pain and reduce swelling. Take an anti-imflammatory medication like naproxen or ibuprofen. You can wrap the ankle during the day with an elastic bandage for support. You can buy ankle braces as well. If it does not improve; see a physician. Wearing good shoes is really important. I found that a good pair of high topped Nikes really helped me with ankle problems.

I hope you feel better

I have sprained my ankle several times playing volleyball.

Any chance you could have banged it without realising? Or even slept on it funny? It's odd for something to start hurting out of nowhere so if this is the case I'd recommend seeing your Dr. In the meantime you can support it with a light compression bandage like a tubigrip and don't do any running about.