That's easy to check.

Turn off everything in the car and pull the ground cable off the battery.
set your multimeter to the highest DC current that it can handle at first.
(Usually 10 amps with a special input for the test leads)
then you measure between the cable you just took off and the neg terminal of the battery. You shouldn't see much at the 10A setting.
Then go down to the lower amp settings requiring you move the red test lead
to another input on your meter. Normal current should be variable .025A
or 25 uA. +- That would be the clock and CPU.
If it's much more, then you start looking for glovebox and trunk lights
and other stuff that's on when they should be off. Post back with the results.

Before you pull the battery cable, check for DC volts with the engine running,
at the battery: You should see at least 14.0 VDC (That checks for charging.)
Note: put the meter probes only on the battery anodes and not the clamps because
sometimes dirty anodes and clamps get resistive and don't conduct current well.
That's we we all have battery terminal brushes ;-)

Warning!!!!! If some helper turns on the headlights or runs the windows
while you are checking current, then you might blow your meter fuse, and
If it's a Craftsman Meter, the fuse is hard to find. Ask me how I know :-(

Bill