This pre-trib rapture doctrine was not taught until circa 1830's...For this doctrine to not have been taught for the first 1,800+ years and now have worldwide fame is scary. Uber scary.
Clearly you have swallowed the anti-Pre-Tribulation-Rapture propaganda hook, line sinker (as have too many Christians). But the facts of the matter are (and I'll leave the Scripture references for now, since you should look them up):
1. The Lord Jesus Christ taught that the Rapture (the catching up of the saints within the Church) would be imminent.
2. The apostle Paul taught the exact same doctrine.
3. The Christians of the first century believed that Christ could come for them at any moment and unexpectedly.
4. Some of the Early Church Fathers held to the same doctrine.
5. Following the rise of the Roman Catholic and Eastern Orthodox Churches, this doctrine was neglected or denied.
6. The Reformers were so focused on the doctrines pertaining to salvation that they simply did not address Bible prophecy properly, and believed with Augustine that the Church had replaced Israel and that the Millennium was already in existence as an indefinite period of time.
7. In the 19th century there were many Christian brethren who turned away from the prevailing ideas about the Rapture and the Second Coming and took a fresh look at Bible prophecy, particularly since Zionism had become a strong movement. Among these men were Darby, Scofield, and many other men who were well-versed in the Bible. Christians (who should know better) revile these men, but they were genuine Christians who had rejected the traditions of men and wanted to preach and practice what was actually in the Bible.
8. Following the establishment of the nation-state of Israel in 1948, many Christians such as Sir Robert Anderson and others recognized that the promises, covenants, and prophecies pertaining to redeemed and restored Israel under Christ would be fulfilled. Thus the majority of evangelical and fundamentalist churches (outside mainline denominations) accepted the doctrine of the imminent return of Christ for His saints as true Bible doctrine.
9. Some fringe groups and some preachers went too far with this and began date-setting, when it was clearly forbidden. As a result they were thoroughly embarrassed when Christ did not literally return and take them to Heaven. The Seventh Day Adventists then started tampering with Bible interpretation to save face and try to justify why their predictions had failed.
10. Those who hold to Covenant Theology and Reformed Theology are confused about these matters, and instead of searching them out from Scripture afresh, they make ad hominem attacks on the men who brought these teachings before Christians.
11. The bottom line is that had none of those 19th century preachers and teachers existed, any Christian could study the Bible for himself and discover that the Rapture is not tied to any Tribulation or Great Tribulation, but could happen today (if the Lord so wished). That is why Christ said "LET NOT YOUR HEART BE TROUBLED".