Jackson says she could barely look in the mirror before she lost weight

Janet Jackson’s dramatic weight gain – a reported 60 lbs., which she has since lost – gave even her pause, she admits.

“I could not believe how big I was, how heavy I really was,” the singer, 40, tells TV’s Extra in an interview airing Tuesday night. “I would see myself in the mirror, but I wouldn’t look too often. I didn’t want to get used to that image.”

Jackson lost the weight through healthy eating and tough workouts – and she’s offended by speculation that she had plastic surgery.

“It does drive me crazy,” she says, “because I’ve worked real hard and I think it’s really easy for (the tabloids) to write it off as (surgery).”

She jokes, “It isn’t hurtful – it just pisses me off. I want to kick some ass.”

But Jackson admits she had some cosmetic work done when she was a teen. “It’s no secret,” she tells Extra. “When I was 16 I changed my nose. Would I do it again? I don’t know. I’ve seen a lot of women that have been pulled and snatched, and it’s not too cute.”

She also talks about whether she’ll marry her boyfriend, producer Jermaine Dupri, 33. “I don’t know,” she says. “If that’s God’s will, then it will happen.”

She’d have children with Dupri, she says: “I would love to with him. Never thought I would. God willing, it will happen.”