--verse 3 is saying, "that day [the subject of the preceding verse--the prophesied earthly TIME PERIOD] will not be present if not shall have come THE DEPARTURE FIRST [our RAPTURE FIRST, the subject of verse 1, now] and the man of sin be revealed" [he is "revealed" when "the Day of the Lord [earthly TIME PERIOD] IS PRESENT" but NOT BEFORE! Not before the INITIAL "birth PANG [SINGULAR; 1Th5:2-3, etc]"]
You have a "private interpretation" (2 Peter 1:20) and a faulty 'translation':
2Th_2:3 Let no man deceive you by any means: for that day shall not come, except there come a falling away first, and that man of sin be revealed, the son of perdition;
2Th 2:3 μη τις υμας εξαπατηση κατα μηδενα τροπον οτι εαν μη ελθη η αποστασια πρωτον και αποκαλυφθη ο ανθρωπος της αμαρτιας ο υιος της απωλειας
It says "apostasia". Apostasy. It points to Daniel 7's little horn, the man of sin and the son of perdition, the mystery of iniquity which was already at work in Paul's day and was to grow after a specific event (Roman Empire began to crumble)
It is the same word used here, and it means to forsake the truth for a lie, to apostatize:
Act 21:21 And they are informed of thee, that thou teachest all the Jews which are among the Gentiles to forsake Moses, saying that they ought not to circumcise their children, neither to walk after the customs.
Act 21:21 κατηχηθησαν δε περι σου οτι αποστασιαν διδασκεις απο μωσεως τους κατα τα εθνη παντας ιουδαιους λεγων μη περιτεμνειν αυτους τα τεκνα μηδε τοις εθεσιν περιπατειν
It (2 Thess 2:3) does
not say in any Koine Greek MS, Codice, Papyrus 'rapture' ([h]arpagesometha) or leaving earth, as the following does.
1Th 4:17 Then we which are alive and remain shall be caught up together with them in the clouds, to meet the Lord in the air: and so shall we ever be with the Lord.
1Th 4:17 επειτα ημεις οι ζωντες οι περιλειπομενοι αμα συν αυτοις αρπαγησομεθα εν νεφελαις εις απαντησιν του κυριου εις αερα και ουτως παντοτε συν κυριω εσομεθα