Sounds like you don't have your spring pre-load adjusted properly. Fill your car with about a half tank of fuel (to get an average weight between full and empty), pick it up, and drop it from about a foot or so onto a flat surface. Slightly push down on the top of the car (maybe a half inch or so) a couple times to get an idea of your car's ride height. You want it to settle with the suspension arms parallel to the ground, or "arms level" as some people say. If your car is lower than this, slide the collars on the shocks down (toward the bottom of the shock) to increase pre-load, and this will raise the ride height at that end of the car. If you have to lower the pre-load collars so much that the spring bottoms out on itself before you reach full compression of the suspension, then you need stiffer springs.

One important note, despite what many think, spring pre-load adjustments do not increase how stiff your suspension is. It just increases the initial tension on the spring, which changes ride height.