I have no questions that God chose me. How can I be so sure? Because I believe in Him and Jesus Christ as my Savior. I could not have come to this belief by my own free will. It can only be explained by the power of the Holy Spirit and God’s grace at work within me.
I am quite certain that He chose me because if God had not chosen me, I should never have chosen Him. And it must be true in my case that He chose me before I was born, because He certainly would never have chosen me afterwards. And I know that He elected me for reasons unbeknownst to me, because I could never find any reason in myself why He should look upon me with such unconditional love.