2004 Corolla CE Battery Draining

I have a 2004 Toyota Corolla with 223k miles on it, and every fews days ill try and start it and it either wont start because of low voltage, or it will be completely dead. A few months ago, if i drove it everyday to charge the battery, it would start every time. Now however even when driving everyday it still sometimes is dead. What could this be? It is on its the third new battery in 3 months, so its not that, the radio has also been checked, any other ideas? Thanks everyone.