Honesty in Relationships. How much is too much

I have been seeing a wonderful man for about a year now and we plan on spending our lives together. I have told him I suffer from mental illness (borderline personality disorder) and I was able to achieve somewhat of balance by the time we met thru rituals of affirmations, meditation, journaling. But i have been so busy and the symptoms are creeping up again.

My bf says he wants to know everything that goes on inside my head. That sometimes I go into dark thoughts and isolate myself. Honestly even if im not having any dark thoughts, i love to be alone some times! But he gets angry when I dont share my thoughts with him.

Do you share everything that goes on in your mind with your partner? I cant keep track of every thought and sometimes it is embarrassing. But he gets so upset! W