Does the questioner feel guilt over her breaking off her previous engagement due to another suitor proposing, and has this caused her psychological distress despite her marriage and having children?

There is no sin upon you for withdrawing from the suitor who proposed to you and accepting the proposal of another, especially if it was merely an agreement and the engagement had not yet been formalized. Each party has the right to annul it, though it is disliked without a valid reason. Strive to forget the matter.