'I confronted my cheating partner. Then my phone pinged with something I never saw coming.'

Transitioning to a long-distance relationship is never easy. It doesn't matter if you are in the throes of new love, or in a relationship that's spanned years.

So when Kate's* boyfriend of six-and-a-half years moved away for a study opportunity, she tried to take it in her stride.

But she had no idea of the pain that was about to come. The betrayal she would discover on her first visit to see him.

Kate's worst nightmare occurred just months after her boyfriend moved away.

WATCH: The number one cheating sign that everyone misses. Post continues below.

"It was my first visit to see him and things felt 'off,'" Kate told Mamamia. "There were all these little signs. I was only there for about four days, and it was literally an hour before leaving for the airport that I discovered he was cheating with the flatmate he was living with."

Upon arriving and stepping into her boyfriend's new life, Kate immediately felt "very unsettled".

Even more concerning though was how unwelcome he made her feel.

"He was quite rude, cold, dismissive. After not being together for a few months you would think he would have been all over me, and it would be a good, fun, happy time, and it just wasn't," she said. "I was quite confused."

Even still, Kate made the effort. She planned dinners, dates, activities for them in his new home; normal things you do to show your partner you miss and appreciate them.

She was stonewalled at every turn.

"He was kind of going about his daily life as he would without me there. I thought, 'where is my quality time,'" she said. "I did voice my concerns, just about not feeling very welcome. I said, 'you should be hosting me here, but if anything, I've been putting in the effort.'"

Even Kate's requests for intimacy were met with excuses.

It was easy to explain those signs away, because the fact Kate's partner was in a share house was new to them.

Before the long distance, they lived together, by themselves, for years.

Over the course of the trip, Kate started to notice a strange dynamic with his female housemate.

"I met the girl he was cheating with. She was 10 years younger than me, which really twisted the knife," she said, adding that she and her partner were both in their early 30s. "He was laughing at all her jokes, he was taking phone calls from her and step outside to take the calls to her.

"There was a moment where we were in his bedroom — nothing physical, fully clothed. And she just comes into the bedroom, breezes on in with a question. I thought 'that's a bit odd.'"

Listen: Unpacking the results of Mamamia's cheating survey. Post continues below.

The moment of discovery.

Things came to a head the day the pair were supposed to fly back home for a two-week holiday together.

"The day we were meant to be flying out, he went to talk to her. He went into her room and closed the door behind him," Kate said. "He came out of the room and I said, 'hey I feel kind of weird, why did this happen? Do I have anything to worry about here?' He said 'no', but I just felt sick.

"I talked to a few friends back home, and they said 'trust your gut.'"

Kate decided to listen to that advice, as well as her body, because she was starting to feel physically sick from the anxiety.

"He jumped in the shower. He left the phone on the bed and I thought 'this is the moment. I have to do this' and I checked his phone," Kate said. "And it was all there, texts between them that confirmed, basically, my worst fear.

"I almost felt that this wasn't real, this is a movie. Your heart rate elevates and you get really hot. My vision went blurry, and I was like 'how is this real?'"

Heartbroken, Kate made the call to fly back home without him.

When she was at the airport, he did something that baffled her.

He transferred her $500.

"I thought 'guilt money. You can't buy my forgiveness,'" Kate said, explaining she had originally requested he pay her back for the $100 she had spent on airport parking that morning.

"I didn't expect that much, he transferred it immediately — I saw that at the airport.

"In terms of compensation, it should've been a lot more."

When Kate got home she was straight back on the dating apps.

"My thinking was, you wasted nearly seven years of my life, I'm not giving him another day," she said.

For anyone who may find themselves in a similar position, Kate has a very simple piece of advice. It's the same advice she decided to follow all those months ago.

"It comes back to trusting your gut," she said. "And another piece of advice I heard just recently, and this is more in relation to dating, but it's also applicable to this situation.

"It's 'don't believe what he says, believe what he does.'"

*Name changed to protect identity.

Feature image: Getty.