Without seeing more context, it seems so. The meaning is not entirely clear.
What's the song? Can you provide the source and more context?

Interested in Language
Hi,
I'm wondering whether the following lyrics are grammatically correct. Should "knew" be changed to "had known"?
If I knew it all then, would I do it again?
Would I do it again?
I'd appreciate your help.
Without seeing more context, it seems so. The meaning is not entirely clear.
What's the song? Can you provide the source and more context?
You will sometimes hear:
If I knew then what I know now ....
Not a professional teacher
Don't rely on song lyrics for good examples of English. Lyrics are written to fit the rhyme and rhythm of the song - the writers have little interest in grammatical correctness.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.
I'm wondering why you didn't provide that link in post #1.
The only relevant question is "Do you think the lyrics should be different?"
I would ask if the lyrics should be changed only if it was my song and I was thinking about changing the lyrics.
(My opinion.)
Not a professional teacher
Thanks for providing the lyrics, raymondaliasapollyon, but to be honest, I'm still none the wiser. I can't work out what she means.
What's rather confusing me is that the following line (If they knew what they said would go straight to my head, what would they say instead?) appears to be a second conditional framed in imaginary general time, making me doubt that the line you're asking about is meant to be framed in imaginary past time. It could also be a similar attempt at a second conditional in general time, making the past perfect incorrect.
Perhaps, like me, you're reading the word then to have the sense of 'at an unspecified time in the past', leading to the interpretation of a past conditional. However, I do wonder whether the comma is misplaced, and whether the correct reading would be If I knew it all, then would I do it again?, making then a resultative, and thereby creating a conditional based in imaginary general time.
I like Billie Eilish and her songs quite a lot but I don't think she's a great lyricist.
Last edited by jutfrank; 02-Jan-2020 at 00:12.