Is a feeling of distress and discomfort after performing Istikhara an indication that the girl is not destined for the young man, and is the young man's change of intention after Istikhara evidence of that, especially with the continuation of the relationship despite these feelings?

The continuation of communication between a young man and woman before marriage is forbidden (haram) and requires repentance. Istikhara prayer is permissible for matters that are not obligatory or forbidden, and it is legislated to repeat it. One should be content with what results from it. The young man and woman are advised to marry if their desire for each other remains and they accept each other in terms of religiosity, character, and appearance, especially given the love between them. However, if this is not possible, it is permissible to withdraw from the engagement, and the man should inform his fiancée of his decision to leave her.