'I found out our baby girl isn't mine while reading my girlfriend's journal.'

It’s probably never a good idea to snoop in someone’s diary – you’re almost guaranteed to find out something that you really didn’t need to know or get your feelings hurt.

For one stay-at-home dad, reading his girlfriend’s diary revealed a shocking secret; his daughter is not biologically his.

“Found out the little girl I was raising isn’t mine when I found my gf’s journal,” a man revealed on anonymous site Whisper. “If I leave, all three of us are screwed.”

18 others also took to the secret-sharing site to tell their stories about finding out they’re not the biological fathers of their children. Their stories range from shocking to surprisingly heart-warming.

One man revealed that his partner deceived him by using a technicality.

“After five years I found out the child was not mine,” the man wrote. “Her excuse was ‘I just said I was pregnant, I never said the baby was yours.'”

Other men were understandably bitter.

"Her excuse was 'I just said I was pregnant never said the baby was yours.'" Image via iStock.

"I know this baby isn't mine," one man revealed. "Just waiting on this income tax cheque and I'm leaving her!"

Some men were keeping the secret for the sake of their families.

"Secret DNA test proves that the baby ain't mine, but that means it's his, and I can't let this little girl have a drug dealing father," one man shared. "I will never tell a soul."

"No one knows but me and my son's mother that I'm not the father," another man wrote. "She cheated on me at a party. I'm 17."

Listen to the Mamamia Out Loud team discuss why they are celebrating the rise of the 'hands-on' dad:

"I will never tell a soul." Image via iStock.[/img_caption]

For some men, finding out that they're not the biological father didn't change their feelings.

"After ten years my wife told me my kid wasn't mine," one man wrote. "I love her and my kid so much, I'm glad she didn't tell me or else I wouldn't have this wonderful family in the world."

"My wife doesn't know that I found out she isn't mine," another man wrote. "It doesn't matter, she's my daughter and nothing will change that."

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