My low self-esteem is my core belief/problem. Having discussed with my therapist my childhood and young adulthood, she attributes this low self-esteem to the bullying and lack of acceptance for my sexuality from my parents and peers that I've experienced as a child. Being 25 now, I don't really think about these moments a lot and haven't done so for at least the last 5 years? And 2-3 years ago I didn't have this low self-esteem issue and was the most confident person ever...

Could I be wrong and indeed my childhood led to this self-esteem issue? If so, then why would I use to have a healthy self-esteem post my young adulthood just for low self-esteem to kick in now?