Hi! Thanks for your reply.
If I use self help, do I need to tell him or should I keep it a secret?
Self help is a great addition to therapy. And I recommend it to anyone who is in therapy as a supplement. You can choose to tell your therapist or not, but sharing what you find may help. You may want to ask him that if you do find things out about your past and how it affects you now, if he is willing to give you feedback about it. He may or may not because of his therapeutic view.