Long ago you went through a long traumatic experience with your peers. You were likely taunted because you reacted to the harsh teasing. Taunting becomes a blood sport for many crewel children and adolescents. It continues because the victim reacts, not because the taunting in itself is true. Often a great deal of the problem is that the taunted person is insecure (as is common in children and adolescents) and they display reactions to the attacks which perpetuate the cruelty. Then, because the victim is insecure, they end up believing that the harassment was (an sometimes is) based in reality. Even when reality is not compatible with the taunting (you have had lots of handsome boyfriends) the emotional scars continue and can be triggered by current events.
Currently when trauma is 'activated', you play a sort of tape in your head of the old emotional hurts. Therapy could likely help this quite a bit. Someone who does CBT might be very useful.
So why do your daughter and your fiancé love you? Because they know you. They know you well, and they know the real you.