If you had sex sex before you are mentally ready and there were negative aspects to it, IE: rape, incest, guilt, then I would agree that it could result in later LD behaviors. But since it was with you and you later married, I question the validity of the therapists claim.
Is there something in her background other than having sex with you at a young age that may have caused the therapist to make this "diagnosis?" Sound like fishing for answers to me.
