our 2001 dodge 2500 has no break lights and it just started doing this

check the brake lite switch on the brake pedal

I had a problem like you describe with my Chevy Silverado. It was my turn signal switch. The test was to see if my third brake light worked. If it works while your rear brake lights don't then your brake light switch is not at fault. Sounds a bit crazy but like I said replacing my turn signal switch (which was a little pricey) solved my problem.