Nobody will be able to prove scientifically the existence of God. But it is possible in theory to prove that God is not omnipotent.
Feeling this way only happens because you are fairly comfortable in life. This gives you the chance to play with all kinds of abstract thoughts.
If the time comes that you have extreme, overwhelming pain or joy, you won't be able to maintain those abstract thoughts. You will know that God exists, even though you will be too side-tracted with your pain/joy to be able to concentrate on figuring out the scientific logic that you now see.
What a nice Guy God is. He gives you such complete freedom, that He doesn't even force-prove Himself to you the only way He could do it... through great pain or great joy. Of course, in the Judgment at the Resurrection, you will readily and willingly accept His perfect judgement for you, whichever way it goes.
