Call him "Jon Casanova" - Jon Gosselin's former nanny says he wooed her with phony promises and cheesy pick up lines. "He put his hand on my face and said, 'Whatever you do, don't fall for me, because it's going to be impossible for me not to fall in love with you.' "

Stephanie Santoro says she and Gosselin had a passionate affair, beginning in July 2009, something he denies.

Santoro says, "He talked about buying a house just down from where their house was and moving my daughter there with me, that way he could stay there."

"So he was promising you the world here," says INSIDE EDITION's Paul Boyd.

"Pretty much," she says.

But their cozy arrangement began to unravel when Kate Gosselin found out about the relationship...Santoro says she tried to reach out to Kate but got no response.

"You slept with her husband, you can probably understand why she's upset with you," points out Paul Boyd.
"Yes but she filed for the divorce."
"So you don't feel like you owe Kate an apology at all?"
"Do I owe her an apology for sleeping with him? No," says Santoro. "Do I owe her an apology for maybe bringing a little more to the table than should be there? Sure."

She said all the bad press was getting to Jon and he actually threatened to commit suicide. "He's like, 'I'm just gonna to end it, I'm gonna end it all, my kids will be better taken care of If I'm not around. My kids will be better taken care of by Kate if I'm dead.' "

Then Santoro says she found out that Jon was cheating on her with no less than two other women, magazine reporter Kate Major and his current girlfriend Hailey Glassman.

"At the beginning of the relationship, now I know, he was with myself, Hailey, and Kate Major," says Santoro. "I can't believe that I was blinded by it, I can't believe that I didn't pick up on it all sooner."

"You're saying a lot of nasty things about Jon right now, why have you come forward with this story?" asks Boyd.

"It's not that I've says nasty things about him...I've spoken the truth. He's a wonderful father, but he's lying."