break lights dont work on my 1999 dodge 3500 dually ive changed switch flasher &turn signal switch what else can it be?

There is a brake light relay you may want to try, and check the fuse.

Have you checked the brake pedal switch?

where would the break light relay be or would it be called something else, I have changed the flasher, the turn signal & pedal switch

The relay would be in a fuse box, may have to refer to the owners manual to see which one, or look it up on line.