Ever since Jon and Kate Gosselin filed for divorce, rumors have swirled about Jon's increasingly wild lifestyle. Though Jon insists he's been faithful to his girlfriend, Hailey Glassman, 22, stories continue to circulate about late nights of partying and hot hookups. And now, In Touch can exclusively report explosive new allegations. Former waitress and single mom Stephanie Santoro, 23, claims that during the month she spent employed as Jon's nanny, she had a passionate affair with the Jon & Kate Plus 8 star in the family home — and saw a side of Jon that's bound to shock even his most devoted fans. In the new In Touch, Stephanie describes her "genuine" romance with Jon — and how it came to a bitter end.

For the full exclusive interview with Stephanie, check out this week's issue of In Touch, on newsstands now.