96 lumina electrical problem

I have a 96 lumina with 162,000 miles on it. I have a situation where on X-mas eve, my car was parked outside our local gas station, I left the car idling and came back out and noticed my dash board lights, my parking lights and my tail-lights were out. I replaced the fuse and they worked for 3 days. Then all of a sudden the fuse blew again. We've traced wires and couldnt find any that were loose or broken or exposed. The fuse blows every 3 days which is weird. So basically its an intermitten short on a circuit that controls my dash board lights, my parking lights and my tail-lights all at the same time. Anybody have any ideas.