This borders on paranoid behavior. It is illegal to record someone without their knowledge. You could be prosecuted. If your therapist will not share treatment notes with you, get a reason why. If you don't find the reasons valid, make a formal request in writing. If you still don't get satisfaction, ask your family doctor or psychiatrist to obtain them. That will work. Secretly photographing notes makes no sense when a physician can obtain them in a matter of hours legally. If you have this much suspicion of your therapist, contact the licensing board and state your case. Let them LEGALLY investigate.