Blinkers and tail lights dim

Lights are very dim on back off truck. When lights are on taillights are even dimer. Is there a brake light switch. Front lights are fine no issues. So I guess it's in the dash, maybe a blinker, or brake switch. Can u help with advice. When I turn on the turn signal they both blink. Say I turn left signal on, the left blinks bright but right blinks dim. If I turn right same thing ( right bright, left dim). No parking lights, brake lights dim, if the driving light is on at night, no lights on the back work at all. The front lights are fine, they work perfectly. Thanks.