This is actually tough, because you are checking if the sprite is overlapping its own type, which is always true, since it overlaps itself!
It would be best to keep your falling sprite separate, even it the image is duplicated (you can Clone a sprite). Otherwise, here's a sample of the logic needed. OverlapFalling.capx
You still need an invisible clone sprite to do the detection, and you need to keep track of the master, so you can exclude it from the overlap detection.
This is using r137, as it have better picking options.