Yes, do go to therapy. You need a professional's guidance here, and regular meetings to help you see your worth as a person.

I liked the comparison to a child molester. This person gained your trust by initially being nice and by being your savior. My ex fiance was nice in the beginning too, before he abused me. I falsely believed he was a good person because he lifted me up when I was down and helped me get past a previous breakup, with another abusive man. He is NOT a good person at all -- he abused me, used me and lied to me. Your situation is no different.