I assume..........that both rear tires are inflated correctly (w/ same pressure). And, both tires are the same size? Believe me, some folks here have pulled some fast ones.
Are you trying to say that, while looking from the rear of the vehicle, it appears to be leaning to the driver's side??
IF you are......that is common. IF you aren't, forget about anything that I'm, posting below.
Figure that, the greater part of the vehicle's life had the "heavy person" sitting on that driver's side (and/or passenger side was empty). Either way.
So, the fix? Well.....new springs. OR, (it may work) switch the springs left for right.
Aloha, Mark
PS.....and, yes.......a broken or worn out shock could also, appear as a leaning condition.