My rear brake light is not working, nor is my blinker at the back right. When I put the right turn signal on it blinks really fast, faster than normal, and the front blinker works. I have replaced both bulbs in the rear and they still do not work.

If the truck is 88 and up there is a circuit board in the rear tail lights that goes bad

Check all four of the turn signal lights. Usually one of the bulbs is bad. Sometimes is lit but not flashing, sometimes it is off. Replace that bulb.
Hope this helps.

Normally with the blinker blinking really fast, it's telling you that one of the bulb is blown, front or rear signals. Check your fuse, and fuse relay to see if it would fix the promblem