You are misunderstanding what Apostle Paul showed about that in Galatians 4:22-31 Scripture about the free woman vs. the bondwoman. Your preacher evidently failed to fully explain it. I will do that here, for those interested, not necessarily just for you... to offer a more complete understanding about it.
Gal 4:22-31
22 For it is written, that Abraham had two sons, the one by a bondmaid, the other by a freewoman.
Paul of course refers to Abraham's sons Isaac in whom God's Promise by Faith was given through, vs. Ishmael Abraham's son by his wife's bondservant slave Hagar.
23 But he who was of the bondwoman was born after the flesh; but he of the freewoman was by promise.
That "promise" Paul speaks of is the Promise by Faith which God gave first to Abraham with The Gospel of Jesus Christ. In Galatians 3, Paul explains that is the same Promise by Faith that all Christians have also believed, and Paul uses Isaac as being the son represented by the "freewoman".
24 Which things are an allegory: for these are the two covenants; the one from the mount Sinai, which gendereth to bondage, which is Agar.
The old covenant, is also what the sons of Ishmael (Arabs) recognized, i.e., the law of Moses. That old covenant represented bondage, as no one could be perfect in keeping the law. It could not save one's soul, even though Paul said the law is good, as it points to righteousness and was to serve as a pointer to the need for Christ's coming per The New Covenant.
25 For this Agar is mount Sinai in Arabia, and answereth to Jerusalem which now is, and is in bondage with her children.
Paul in the above is referring to this present world Jerusalem and the orthodox Jews who still try to keep the old covenant, as they reject Jesus of Nazareth as the prophesied Messiah.
26 But Jerusalem which is above is free, which is the mother of us all.
That Jerusalem which is above is the Heavenly Jerusalem that will be established WHERE? Of course it is in the Heavenly right now with The Father and The Son, but WHERE does Revelation 21 reveal its final resting place will be?
Rev 21:1-3
21 And I saw a new heaven and a new earth: for the first heaven and the first earth were passed away; and there was no more sea.
2 And I John saw the holy city, new Jerusalem, coming down from God out of heaven, prepared as a bride adorned for her husband.
3 And I heard a great voice out of heaven saying, "Behold, the tabernacle of God is with men, and He will dwell with them, and they shall be His people, and God Himself shall be with them, and be their God."
KJV
In final, the Jerusalem that is free, which Paul spoke of, is to come down to this earth, out of Heaven, and The Father also will dwell with us, ON THIS EARTH, meaning this SAME EARTH HE WILL RESTORE TO ITS FORMER GLORY.
Gal 4:27-31
27 For it is written, Rejoice, thou barren that bearest not; break forth and cry, thou that travailest not: for the desolate hath many more children than she which hath an husband.
Paul points to the allegory in Isaiah 54, which I have tried to explain to brethren several times. The barren woman represents those who remain faithful waiting for Jesus to return. But the married wife represents those who fall away to the false-Messiah that will come first. Those of Faith are represented by the "chaste virgin" idea by Paul in 2 Corinthians 11, and in final will have more children (i.e., the Gentile believers joined with God's chosen elect).
28 Now we, brethren, as Isaac was, are the children of promise.
29 But as then he that was born after the flesh persecuted him that was born after the Spirit, even so it is now.
To this day, BOTH... radical sons of Ishmael (Arabs) who follow the law of Moses and Mohammed, along with unbelieving Jews, work against those in Christ Jesus.
30 Nevertheless what saith the scripture? Cast out the bondwoman and her son: for the son of the bondwoman shall not be heir with the son of the freewoman.
31 So then, brethren, we are not children of the bondwoman, but of the free.
KJV
In Summary:
The fact that those in Christ are represented by the FREE woman, with the Heavenly Jerusalem that will eventually come down to this earth out of Heaven, means we await Christ's future return and the glory of the world to come. We await that, instead of THIS present world time and today's Jerusalem on earth, which is in bondage still.
This means a MAJOR FUTURE CHANGE FOR THE EARTHLY JERUSALEM THAT EXISTS ON EARTH TODAY.
It is NOT ABOUT US GETTING RAPTURED TO HEAVEN. That Revelation 21 Scripture is clear that the new Jerusalem is coming HERE, ON THIS EARTH, but a restored earth. Even the Revelation 21:16 verse reveals God's Heavenly Cube will EXTEND from the base of the earth where new Jerusalem will be, and go upwards and outwards 12,000 furlongs, forming a cube.