If you have a towing package with a trailer wiring harness, the short could be in it as well, since it plugs into the brake light wire. But agreed ^^^ you have a short. Maybe a bad ground off the rear lights.
My brake light fuse keeps blowing as well, 99 ram 1500 with the 5.9. I was just wondering what you found out to be your problem? Mine will work for a while but randomly blows. I plan to re do the connecters that hook into my trailer plug but wanted to see what you found before I blindly track the gremlin.. Thanks