I told my guy something deeply personal that was to remain between us. I specifically asked that it not be shared with anyone. I accidentally overheard a voicemail from his Aunt who is like his Mom and she was asking him what to tell me if I called her after he broke up with me due to what I told him! The big secret was mainly about my finances which, at the time, were pretty dire and I wanted no one but him to know about it because it was embarrassing and I trusted him and confided. I never thought he would break up with me as we were madly in love and talking marriage for almost 2 years. I ended the relationship first because I was so let down and worried that he would go and tell her everything about me. Apparently he didn't want to break up afterall but now I just don't like what he did, nor do I trust him.
Also, I felt betrayed.