Break lights on my 95 silverado
 

My break lights are not working but my third break light is working.I have parking lights, both blinkers back up and hazards work. When I hit the break pedal with hazards on they keep on blinking and dont stop like they should. I found a white wire that I think is for the breaks that is hot (working) near the axle. It lights my test light when the break is on and goes off when it is not. Could it be a fuse, like the flasher fuse or break fuse? Is there a way to test the fuse or can a parts store test them. THANKS FOR ANY ADVICE.