Help! My car rocks back and forth

Today I was driving about 50mph and i felt like i was floating back and forth. Like swaying back and forth. Could it be..........

Unbalanced wheels (mine are but i lost one of my weights)
Shot shocks
Tire Pressure

Or what??

Please tell me!

thrown down some more info.....maybe someone can help, but we aint got much to work with

can you describe the problem a little more specifically? what axis is the "swaying" in (longitudinal-fore/aft, laterally-side to side, or diagonally-dutch roll). Did it only occur at one speed or was it noticeable at other sppeds just less intensely? what frequency is the swaying?

It rocks laterally side to side. When Im going slow its not as bad, but one time was i was above 120 i could hardly control the car. The steering wheel starts moving left and right, not the whole column i mean like the wheel moved 45* left and right and i could hardly control it.

Make sure your tires have the right air preasure in them.

other then that it sounds like the road driving the car.
by that I mean cause of hte wider stickier tires generaly on Fbodies the ruts in the road grab the wheels and make the car go back and forth inside these ruts, the stickier and wider the tires, the worse it is.