You have a current draw you need to track down. Turn everything in the car OFF and DO NOT try to start it with the VOM connected. Take a VOM and put it in the batt circuit. Pull the NEG batt cable and hook your VOM + lead to the Batt - post and the NEG VOM lead to the clamp of the NEG cable you just removed. Set your VOM to the smallest Amp setting. You should see if there's a current drain. Start pulling fuses one at a time til it stops and track it from there.