YOU SAID:

if you had done that then I might not have done it

INTO JAPANESE

あなたがそれをしたならば、私はそれをしなかったかもしれません

BACK INTO ENGLISH

If you did it, I might not have done it

INTO JAPANESE

あなたがそれをやったなら、私はそれをやっていなかったかもしれません

BACK INTO ENGLISH

If you did it, I might not have done it