1994 chevy silverado battery seems low (dead) every few days

I have a 1994 checy silverado 2500 with 3 year old battery, alternator, and starter. I left the car for a week and came back and the battery was dead and needed a jump start. Charged up and sat for 3 days and dead again. I check for lights on and nothing. Any ideas?
Thanks for the help

Look for any accessory that is not working, like a power window. Sometimes this will be the root cause of the parasitic drain on the battery.