This is common. You're opening yourself up, in an intimate way, and realize he knows more about you than anyone else. You're telling him things you wouldn't share elsewhere. You confide in him because you trust him. You trust him because he doesn't judge you. Trust is the first building block of love. What you're feeling is a natural attraction and nothing to be ashamed of.

Addressing these feelings are another issue altogether. Wish I could provide a simple answer.