Your situation is different from many adoptions in that the first parental figure in your life was harmful to you. I'm very sorry that this happened.

When the relationship between parent and very young child is safe and healthy, the child develops what is known as a secure emotional attachment to the parent. Unfortunately, you could have learned, at a very young age, that it is dangerous to try to attach emotionally to parental figures. You could have learned that parental figures hurt you and then disappear. You might well then tend to avoid emotional attachments to parents.

To work on this in therapy, I would suggest trying to find a therapist who is familiar with attachment theory.