You need to test for a drain, simple to do, pull all the fuses out for the car, connect a bulb between a battery post and the cable that you took off it, watch the bulb as you put each fuse back,(use a low wattage, say 5 watt bulb) as soon as the drainy circuit is refused it will glow brighter, make sure you have the doors shut though, and a front window open.
It should on a healthy battery last weeks as already said.
tabetha