First, you have to determine what asymmetry existed vefore your surgery. This can be the volume, dimension, position,relative position of nipple to breast, relative position of breast to chest, amount and elasticity of skin, etc., etc.
Second, the placement of the implant will not always, and in fact is rarely, perfectly symmetric often with one sitting a little higher or lower, or more medial or lateral, than the other. This can change over time as the implants move over the chest wall. This asymmetry is more evident the less breast tissue you have to camouflage these imperfections.
Finally, breast augmentation is a dynamic procedure in that there is settling, contracture, and tissue relaxation that occurs as well as the constant effects of gravity and movement.
The question is not that asymmetry exists, but how noticeable it is, how much it bothers you, what is causing it, and whether or not it is correctable. Continue to follow up regularly with your surgeon as often you can tweak your results with post-op therapies. Be patient and don't look at your breast too closely this early on.