It's appropriate to discuss anything in theapy that causes you psychological discomfort or real struggle. It's not so much a question of appropriateness as the simple fact that those types of things are difficult to reveal to the other person. You may start just by saying to your T that there are things on your mind you feel you need to talk about but they are very difficult to talk about and then let him do his part to make it more comfortable for you to discuss them. Good luck.