"I have got to figure out what's wrong with me for them," Danielle Busby says in a sneak peek

As Danielle Busby continues to battle a mystery illness, she's hopeful she'll find answers — not only for herself, but also for her young daughters.

In PEOPLE's exclusive sneak peek at Tuesday's episode of OutDaughtered, Danielle comes home from a doctor's appointment wearing a heart monitor, which she first shows to husband Adam before revealing it to their six girls: 6-year-old quintuplets Ava, Olivia, Riley, Parker and Hazel and 10-year-old Blayke.

"I came home with a heart monitor," Danielle, 37, says to Adam, pointing to the white medical device on her chest. "At least it's not connected to a wire and a box, and it's going to beep all night."

She explains that the heart monitor — which adheres to her skin and measures her heart rate — will be taken back the following week to the doctor, who will "download what it records, and then we'll go over all the results together."

Seeing his wife wearing the monitor for the very first time, "I mean, you can't help but be taken aback by it a little bit," Adam, 38, tells cameras. "Just because it definitely makes it a lot more real that this could potentially be something wrong with her heart."

"It's kind of crazy to see you like, wearing a heart monitor," he tells Danielle, who says she was the "youngest person in that whole building" when she went to get the device.

"The cardiologist did a bunch of tests, and I'll get all those results when I go back with the heart rate monitor next week," she adds.

Having a house full of little ladies who observe their mother's every move, Danielle and Adam decide to sit their girls down to explain what the monitor is for.

Danielle Busby
The Busby family
| Credit: Danielle Busby/Instagram

"I know I have to tell the girls what's going on because they notice any little thing. 'You got new earrings.' 'You got your nails painted.' I mean, at some point they're going to notice and see this big, white, bulky thing on my chest, so we're going to tell them what it is, what it's for, what it's doing," she says in a confessional.

But although the TLC star wants her daughters to understand that she's been going to the doctor, she doesn't want "to scare them," she adds. "They're pretty young, and more panic for them means more stress for us."

Calling the girls downstairs, the mother of six gathers the family at the dining room table, where she showcases the heart monitor.

Danielle Busby
| Credit: TLC

"What is that?" they ask.

"It's going to keep track of my heart rate," she explains, adding that it's "to make sure [my heart is] okay."

Danielle Busby
| Credit: TLC

As the girls seek more information, Danielle tells them her "heart beats kind of weird sometimes. And so they want to make sure it's okay. So I had to go see the doctor and then they put this on me."

The Busby's eldest child, Blayke, then poses a serious question: "What will they do if it's not okay?"

"We don't know," Danielle admits.

Danielle and Adam Busby's daughters
| Credit: TLC

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Knowing her girls are concerned for her isn't easy. "It crushes me to see my kids' faces of concern because I don't want them to worry about me. You know, you're my little girls and I can't tell them 'everything's fine,' because it's not," Danielle says to cameras.

"But it definitely gives me that motivation to find an answer, because this isn't just for me," she adds. "I mean, it's for my family. I have got to figure out what's wrong with me for them."

OutDaughtered airs Tuesdays (8 p.m. ET) on TLC and is available to stream on discovery+.