The first thing that I would do is to be honest with your therapist. I know that is hard to do but it is important that s/he know what is going on with you. My guess is that s/he has heard worse before-there is nothing new under the sun. If you cannot bring yourself to tell him your secret right away you could tell him there is more to the story --and you are working on being able to tell him.

Good luck--it is truly horrible to feel alone in our misery.