Allegations against Collins surfaced after an audio recording of him speaking candidly (in what was supposed to be a confidential therapy session) about molesting the girls was released in October.
"I didn't want to have to deal with these things publicly," the 7th Heaven star tells Couric.
Earlier this week, Collins released a statement saying he "did something terribly wrong" and has been "working to atone for" his actions in the years since.
The actor tells Couric that he relied on the church and his Christian faith to deal with his past. "One of the main things about the Christian faith is, Christ says in so many ways, 'Bring me that about you which is broken. Bring it,'" Collins tells Couric. "And most people are broken in some way."
Collins' full chat with Couric will air on ABC's 20/20 this Friday. Watch a teaser below: