Your problem usually stems from concentrating on the fingers. Instead be aware of your upper arm.
Consider this: efficient movement always goes from the centre of the body to the periphery. So, instead of trying to hit a note with your pinky (or any other finger for that matter), use your upper arm to position the fingers. Because the muscles in the arm are so much more powerful than the muscles that move the fingers, it will be much easier, you will never get tired, and you will be unlikely to get injuries. If you hold your arm outstretched in front of you, and move your hand from side to side by using the upper arm, you will immediately see that a tiny effortless movement of the upper arm causes a considerable movement of the hand. Now compare the same movement by using your forearm to initiate it. See how much more effort and range are needed to accomplish the same result.
Most horizontal movement on the piano should start at the upper arm. So your problem is to calibrate the upper arm movements (remember, tiny movements will have huge effects at the hand level) in order to position your fingers accurately. Then you will have to co-ordinate the finger movements with the arm movements. It seems complicated, and it is - but only to describe and understand. In fact it is fairly simple to do because we are naturally built to work in this way (movement starts at the centre as tiny movements that amplifies to the extremities).
Also bear in mind that these things are very hard to describe properly in writing, and even more difficult to follow from the written account. So find someone who knows about this stuff, and ask him/her to demonstrate and guide you.
Best wishes,
Bernhard.