short somewhere?

Using your voltmeter won't tell you much of anything. You need to switch it to the DC ammeter which measures current flow in amps or more likely in microamps. Disconnect one of your battery cables and put the ammeter in series (one lead to the battery and one to the battery cable.) and see what it's drawing. It should be zero or if you have an aftermarket radio it may be drawing microamps of current just to keep the RAM on the radio alive. If it's drawing quite a bit isolate the circuit by pulling fuses as stated above. I once found I had a current draw due to a glove box light not turning off in which case it was drawing milliamps of current and would drain the battery in 2 days.