Anyone who has been cheated on in the past will be all too familiar with that gut-wrenching feeling you get the moment you find out.
It's a mix of betrayal, deep hurt and blood-boiling anger as you try to process the news, and depending on how you catch your partner's infidelity, screaming matches can ensue or silent tears fall.
There's no easy way to find out that your partner has been up to no good, but one man has certainly been met with one of the more unusual conundrums, as he's caught his girlfriend in a lie thanks to his own secret.
The bloke has claimed that his girlfriend cheated on him, and he's quite sure of this allegation, as the woman has told him that she's pregnant without knowing that he had a vasectomy - making it impossible for him to be the father of the child.
The anonymous man wrote to the Daily Star's agony aunt Jane O'Gorman to seek advice as he's unsure on how to approach the subject with his seemingly unfaithful partner.
He said: "My girlfriend has announced she's pregnant and I’m about to become a father.
"The only problem is that I had a vasectomy two years before we met".
The boyfriend continues to say that the woman has claimed that their contraception didn't work - but he's not convinced, as he writes: "She's lying. She's obviously been having sex with another bloke".
This isn't the first red flag in their relationship, as the man has struggled to trust his partner before.
He explained: "I've had my suspicions for ages. A few months ago, she started wearing fancy outfits to work and coming home late.
"Over the summer she announced she had a training weekend and I guessed she was going away with a secret lover.
"I'm so disappointed. I thought she might be the one. How long should I make her sweat?"
Advice columnist Jane said: "This is not a game. You have to tell her the truth straight away, so she can decide what to do about the pregnancy.
"I understand that you're upset, but don’t waste any more time. Explain about your vasectomy so that she understands that the baby cannot be yours."
Jane explains that the woman needs to tell the other man about the baby if she has been unfaithful, and urges the boyfriend not to wait too long to confront her.
"It's time that everything came out in the open. She may have let you down and disappointed you, but you cannot leave her in the dark because this is too serious."
Do you have a story to share? We pay for stories. Email us at yourmirror@mirror.co.uk
