I bled both sides of my front brakes today. When i finished, the brake pedal of the trunk still went all the way down to the floor. Do i need to bleed the rear breaks as well? Thank you

 

Why are you bleeding them? Did you do any work? If you didn't open a line and it just started going to the floor you either have a leak or a failed master cylinder.

 

X2. Most vehicle's brake lines are crossed meaning a front corner is tied to the opposite rear corner and vise versa due to safety and failure issues. You're supposed to bleed brakes from the farthest corner away from the master cylinder working your way to the closest corner, and technically by the book a lot of vehicles these days you have to use a scanner which activates the hydraulic control unit by opening and closing the valves in a certain sequence following a procedure for proper brake bleeding. But back on point if you don't have an external leak anywhere, start the truck and hold your foot on the brake pedal as if you're sitting at a stop light, if your foot slowly starts creeping to the floor more than likely your master cylinder has an internal leak which means the piston cups are no longer holding the fluid pressure and its bypassing.

 

I don't know what year the OP's truck is but I just changed all of my lines on my 92, the front are seperate from the rear. It's an old school simple system. Still need more info. I agree tho, I always start at the farthest wheel from the master and work my way to it.