Jason Collins says that he regrets not telling ex-fiancee Carolyn Moos that he is gay.

Collins, 34, is the NBA free agent who came out gay last week in a cover story for Sports Illustrated, making him the U.S's first openly gay professional athlete.

Moos and Collins dated for 8 years and a planned wedding was called off in 2009. The 34-year-old Moos, a model and a personal trainer, also played basketball professionally in the WNBA.

In a clip from Oprah's Next Chapter broadcast Sunday, host Oprah Winfrey asks Collins if he would have followed through with marrying a straight woman.

“I hadn't reached acceptance yet in myself,” Collins says. “It was deep down like, 'Jason, you can't go through with this. You're going to be ruining her life and your life. And leading to a life of unhappiness.' I'm still trying to process it but ultimately I did the right decision.”

“Now, I wish that I would have, you know, told her [the] complete truth at that time. I wasn't there, yet,” he adds. (The video is embedded on this page. Visit our video library for more videos.)

Moos said in a CNN interview that Collins only recently told her he was gay.

(Related: Carolyn Moos, Jason Collins' ex-fiancee: I invested 8 years.)