What does he actually mean from our conversation? Why am I the one who seem to be trusted compared to the other? Why am I the "ONLY ONE"?

A part of our conversation goes below here.. (Note - it's revised a little):

Him: I trust you so that's why I tell you.
Me: Why?
Him: Because you're the only one.
Me: But you still have M*******.
Me: She seems to have more of your secrets than I do.
Him: Not that much.