Conventional shocks (not gas filled) have no lifting effort, they only produce a hydraulic dampening effect. If your shock were badly worn it causes the springs to flex too much and weakens them, if you had one bad shock it would weaken that spring over time, this happens over time, its not going to happen in a week or a month. Back to your problem, to really measure this, all the tire pressures must be the same (a little higher than normal like near the maximum pressure your tires are rated at will reduce tire flex), then you need to be on a almost perfectly flat and level surface (if you have a long level and a straight 2by4 you can check this), if you are measuring it on a surface that is not then you should try to find one. If your car has a lot of rust in the suspension areas this could cause problems, if your car has been in a collision previously the body shop may not have straightened the unibody out, and you could have some weak springs. How much lower is it on the drivers side, is it at the front or the back or both, if it is only like an 1/8" or maybe even up to a 1/4", I wouldn't worry with it as long as the car drives okay. Suspensions are a little tricky, for instance, if the left front is low, the right rear should be high. Good Luck.
