Jesus said, "Immediately AFTER the tribulation of those days shall the sun be darkened, and the moon shall not give her light, and the stars shall fall from heaven, and the powers of the heavens shall be shaken: And then shall appear the sign of the Son of man in heaven: and then shall all the tribes of the earth mourn, and they shall see the Son of man coming in the clouds of heaven with power and great glory. And he shall send his angels with a great sound of a trumpet, and they shall gather together his elect from the four winds, from one end of heaven to the other." - Matthew 24:29-31.
Matt. 24:31 tells the same thing with 1 Thess. 4:15-17, when Christ shall come, the trumpet shall sound, and we all shall be caught up together to meet Christ in the air. That will be follow after tribulation.
Bible teaches us that, we must go through much of tribulation first - Acts 14:22. And 1 Thess. 3:3-4 telling us, we are appointed for tribulations. Because, Christ already suffered tribulations first - John 16:33.
There is no promise in Bible that we shall escape from tribulations and persecutions. Because, CHrist already suffering them for us, so, therefore, we should follow His examples - 1 Peter 3:21 and John 16:33.
Bible teaches us, that, Christ shall come again - once, not twice.
That why I reject pretribulationism doctrine, because of it is unbiblical and men-making doctrines. I rather follow what the Bible saying what men saying according Col. 2:8.
In Christ
Rev. 22:20 -Amen!