So when you sin, you become "out" of Christ? You lose your salvation that you had at birth? That won't work. Sorry brother.
Amy, we are just like Adam and Eve. Adam and Eve were made upright, and Ecc 7:29 says all men are made upright.
When Adam and Eve sinned, they spiritually died right then and there. They did not physically die until centuries later.
When Adam and Eve believed God's promise to send a Saviour they were saved, God then took skins and covered them representing the righteousness imputed to us. Now they were alive AGAIN.
Here is the promise made to Adam and Eve.
Gen 3:15 And I will put enmity between thee and the woman, and between thy seed and her seed; it shall bruise thy head, and thou shalt bruise his heel.
Here is Adam and Eve being covered by the skins. Blood had to be shed.
Gen 3:21 Unto Adam also and to his wife did the LORD God make coats of skins, and clothed them.
How do we know Adam and Eve believed the promise? It is shown in the next chapter.
Gen 4:1 And Adam knew Eve his wife; and she conceived, and bare Cain, and said, I have gotten a man from the LORD.
Eve was mistaken, but she believed Cain came from God and was the promised Saviour. She had faith in God's promise. When they believed they were made spiritually alive again. However, their body was still under the curse and they died physically many years later as we all do.
"In Adam" is said only once in all the scriptures (1 Cor 15:22). This entire chapter is speaking of the physical resurrection of our bodies, not spiritual. All men are "in Adam" physically and all die, even innocent babies.
Being born of Adam does not separate you from God, sinning separates you from God.
Isa 59:2 But your iniquities have separated between you and your God, and your sins have hid his face from you, that he will not hear.
How can our sins separate us from God if we are born separated from God because of Adam's sin?