I went through this a few years ago with the suicidal ideation, as they already knew about the self harm aspect (which I didn't actually tell them about). To me it is always hard to open up to someone with something that feels so personal and taboo. Especially my shrink, because I have a tendency to want to make everyone think that everything is perfectly OK when it is not. I don't remember exactly how I said it, but I am glad that I pushed myself out of my comfort zone to tell him.

Anyway, my best advice is to just tell him to the extent that you feel you are able to. In my experience, any session usually starts with "how have you been". This allows for you to begin by saying how you have not been feeling great or have been having a hard time. Usually they will inquire about it and ask follow up questions, which provides the perfect opportunity for you to open up and tell him. It is a hard situation to deal with, but it is important to speak with someone about it.

While this advice is easier said than done, don't be afraid or ashamed to reach out. Don't forget that he is there to help you. He has been trained to listen, be nonjudgmental, and provide assistance to people in our situation.