"I felt sick." Bachelor in Paradise's James Trethewie on learning that Alex liked Bill.

On Tuesday night, one of Bachelor in Paradise’s love squares became a triangle.

After witnessing Alex Nation form connections with both Brooke Blurton and Bill Goldsmith, James Trethewie decided to walk out of paradise.

Speaking to Mamamia, James said he made the decision after Alex hooked up with Bill in front of him.

“I’d been told they were just friends the whole time, so I didn’t know anything,” he explained. “I’d been away for quite some time and I walked back in and it was sort of ‘boom’, and I just thought ‘what is this?'”

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“I knew about Brooke early on and was really supportive of that, but it was the Bill thing that wasn’t transparent,” he added.

For 33-year-old James the biggest betrayal was not knowing the pair had feelings for each other before they acted on them.

“Bill was sharing my hut with me and he’d snuck out to go into her room, I sort of felt sick and couldn’t sleep all night,” he explained.

“I think if you don’t know it just kind of catches you out of the blue.”

The bachie alum said he and Alex had a much deeper connection than what we saw onscreen. They even had a date during the first cocktail party.

“When she came in I was empathising with her situation. You know, to walk in and have you ex in there. She had said ‘I broke up over text and we haven’t spoken since’,” he explained.

“So I was like ‘I’ve got your back, you’ll be OK’ and I was very supportive through that and I guess we connected early on.”

But once she become closer with Bill, James realised paradise wasn’t for him.

“So I was just like look, you know, you need to explore and see what you’ve got with everybody,” he said. “You do you, but I’d have to change who I am to stay in here and adapt to this situation.”

“I’d have to start exploring with multiple people and I just don’t want to do that.

“I watched last season and I think that people just connected with one person and hung out. I was hoping to do the same thing but there were a lot of love triangles, squares, going on in there and it was a bit hectic.”

The financial adviser made the decision to leave paradise the morning after Alex and Bill spent the night together, but he had to wait until Alex came back from her date with Brooke to tell her.

Looking back, he doesn’t regret his decision.

“I think what I’m proud of the most is having integrity and morals the whole way through and it was absolutely the right time for me to be going.”