'98 silverado, brake,tail lights problem HELP

My brake and tail lights just quit. Turn signals work but blink quickly. If the left turn signal is on and you step on brakes, the right turn signal starts blinking and vice versa???? I've changed all the bulbs and checked all the fuses. Anyone have any ideas??

I would try new circuit boards in the tail/turn/brake lights! I don't know if it is possible but they could be shorted and back feeding pwr to the other turnsignal when the brake is depressed. These are problematic about shorting out.

If you have a trailer connector, make sure none of the pins inside are touching eachother

I would do as J-Ri suggests and look for wires touching each other. Also, a lot of very weird electrical problems are caused by a bad ground, or lack of a ground. Check and make sure your grounds are clean. Also check the main chassis grounds and battery ground. For a simple test, run a small ground wire right from the battery to the light socket and see if that fixes the problem.