just throwing sticks, but check your brake switch. i've read a lot about how the brake switch eiither makes the brakes stay on the entire time or how it makes the brake lights not work at all.
Probably the little rubber/plastic piece that goes on the brake switch broke. Happened to me, I found it on the floor of the car in pieces and didn't think anything of it since I didn't know wtf it was. Next day I had a dead battery.