Not an infj, but I relate to what you're saying. Trust is important in all types of relationships. In my opinion, if an infj doesn't have trust, there is no relationship and they will want to pull away and disappear but they also are deeply concerned for the other person and don't want to be the one to inflict negative feelings of any sort. So, even if they don't believe that the relationship has any merit, they will continue on with it for the other person's sake till the infj can't live with the lie any longer.
Also I hear infj's feel extremely vulnerable after sharing intimate details of their lives, and depending on the reaction of the person they share with, will either deepen the relationship or make an infj shut down completely.
Welcome to the forum, by the way.