Battery caps are popping off

[GreenMystChevy]

First off, my truck is an old beater that gets me around from place to place. Well, one day while driving down the freeway I hear this bang against the bottom side of my hood. I pull over and find that one of my battery caps had shot off so hard that it hit my hood and I heard it. Well, not being real smart or much time, I continued to drive it for a week only to realize that my battery had shot both caps off and was spraying battery acid all over the place. I had to get to work so I threw in a brand new Optima and when I got to work it was hissing pretty loud.
What is going on here, is it just a short somewhere, am I going to blow up my battery, etc? I know I need to get this taken care of ASAP because I think I have a potential bomb under my hood.