If you can test the current drain whilst the car is not running with the alarm on and off, then that'll give you a better idea of what's going on. If you can't do this yourself, then any electrician should be able to check this with a multi-meter in a matter of a few minutes.
As I said, mine draws around 50mA with the alarm on. My alarm is a Clifford with quite a few sensors, so it possibly takes a little more current than a more basic alarm.
Some time ago I found two trackers concealed in the car. They were also drawing current, which didn't help. You could also have a tracker hidden away somewhere.