After finally spending a night with boyfriend Mike, Ximena has a major bombshell to share with him.

In PEOPLE’s exclusive sneak peek at Sunday’s episode of90 Day Fiancé: Before the 90 Days,Ximena is talking to sister Wendy about Mike, who traveled to her native Colombia to meet her for the first time.

“Do you want him to propose to you?” Wendy asks, to which Ximena says, “If Mike proposes to me, of course.”

However, Ximena has a secret that she hasn’t yet told Mike.

“Does Mike know that you can’t have kids?” her sister asks before Ximena shakes her head no.

TLC

Before the 90 Days

Ximena adds, “So I decided to get operated on and they cut my tubes and burned them, so that I definitely couldn’t have more kids.”

Never miss a story — sign up forPEOPLE’s free daily newsletterto stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human interest stories.

“What do you think he’ll say?” Wendy asks.

“I can’t imagine that. It’s going to be a hard blow for him because he’s excited to be a dad. That does hurt me a lot,” Ximena admits.

Before the 90 Days

She says that though she should have told Mike earlier in their relationship, she wanted to meet him first.

“I know it was a mistake not to tell him the truth earlier,” Ximena says in her confessional. “But I wanted him to come to Colombia so we could see each other first and to tell him in person, not on the phone. But I feel super nervous because I feel like I love him. So for me, it would be fatal if he ended it and left.”

Despite her nerves, her sister advises her to tell Mike right away. “You have to tell him because in a relationship it’s always important to have trust,” Wendy says.

“I have to talk to Mike about it. I’ll do it tonight and I hope Mike understands,” Ximena concludes.

90 Day Fiancé: Before the 90 Daysairs Sundays (8 p.m. ET) on TLC.

source: people.com