I'm Perplexed! My bed now has a "taco lean"

WTF!
for about the past month i noticed my bed has a slight lean to the right. the front of the bed is even on both sides. the back of the bed is about 1/4-3/8" lower on the right. and my bumper slightly shifted to the right.
There is ABSOLUTELY NO DAMAGE to the body or bumper. i have inspected all of it just short of a microscope.
i am gonna fully inspect the mounts and attachment points later today. i'll get some pics for everyone and measure everything exactly.
anybody with knowledge of the rear attachment points have any ideas?
thanks

08 DC short bed, leaf spring TSB, 5100s, 17k miles

 

Have you done any towing or hauling lately?

 

Ive heard of some people having parts of the plastic bed near the tailgate crack and cause sagging, Hope its nothing. Good luck!

 

i have never towed with it. haven't hauled anything too heavy.
the only thing i can think is that i was parked on a drop off with my left rear tire hanging over and my rt rear wheel holding up the rear for about 30 min.
is that likely that my right leaf is sagging a little?

**my bumper has always slightly been shifted right**

 

heh probly, the springs on these are weak. Park it the other way to even it out?

 

the frame and the rear suspension are level. the front of the bed is level. the right rear is 3/8" lower than left rear. no damage anywhere. no wrinkles. no nothing. WTF!
anybody have a parts catalog pic with a diagram of the bed?