ya something could be draining it. I did this test to see what it was on my old car a while back, but im tryin to remeber exactly how i did it. I beleive this is how to check whats draining your battery, but correct me if im wrong because i could be.

So when the cars off and all accessories off get a test light and unhook your battery ground cable. Hook up the ground on the test light to the ground cable and then the psotive of the light to the positive cable thats still attached to the battery. If this lights, then theres something draining it. You have to keep the light on there in place and pull each fuse out one by one, then place it back in,waiting for the light to go out. When you pull a fuse and the light goes out this would mean that one of the particular things on that fuse is draining your battery. Worked for me on my 87 Audi, cant see it not working for you. Give it a shot and someone correct me if those steps are wrong.

 

I think it's ground to ground cable, and positive to ground electrode of battery.. So that light is in between battery and car circuit..

I don't have a light. Can I use a volt meter instead?

 

ya that is it. But ya, you should be able to use a multimeter also. Just look at it and watch for the numbers to drop when you pull the fuse, instead of watching for the light.

 

If you use a meter, i would set it up for amps. If the leads are reversed it will readnegative. This way you can really see whatgoing on.