as bear said, get your battery tested.
but modern vehicles like this do have a certain amount of "parasitic draw" like that, which will run your battery down over time. but a week shouldn't be long enough to run it down.
if you don't notice any obvious problems, you might consider hooking up a very low output battery charger, i think one common brand is the "battery tender", the goal is to keep it from going dead because we all know that running a battery dead is a sure way to kill it permanently, and at well over $100/battery, we hate to do that!