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"I'm not sure we should go through with this," says Cena, before the episode cut to black.

Nikki Bella and John Cena's decision to call of their engagement shocked fans in April, and now "Total Bellas" viewers get to watch the unraveling of what they thought was a rock-solid relationship.

Although it looks like the couple might possibly be reconciling IRL, the two were put through the wringer on Sunday's new episode.

It was one thing after another this week, as Nikki realized how much being a mother means to her and struggled to enjoy her engagement party or wedding dress shopping. It ended on a cliffhanger, with Cena questioning whether they should go through with the wedding.

Here are five telling moments of tension the cameras captured tonight.

Best Man Mix Up

Nikki confessed that she already picked out a best man for her fiancé, without consulting with the groom-to-be at all. "So, I may or may not have kinda jumped the gun and told Rob that he's your best man. I just assumed that if you were to have two best men it would be Rob and Johnny Martin," Nikki admitted.

"Now saying it, I kinda feel silly. Maybe I should have said this out loud before I actually did it," she added in a confessional, before the camera cut to Cena's less-than-enthused face.

After Cena asked if she just thought the two man would be his choice or if she actually talked to either of them about it, she added, "It's not like I gave them a gift and I was like, 'Hey it's official.' I just said you'll be John's best man." John's response: "That's pretty official to me, saying that they have the job, right?"

She attempted to alleviate the situation by joking "it's like I blew Christmas," but Cena was still clearly frustrated. "This is no time for us to argue," Cena said. "This is a big thing for us, so I'll just say what's happened to far: You took that choice away from me and you took the meaning of me telling them."

"I guess what I'm trying to say is, one, let me know if you're going to make a decision on my behalf, especially one that directly affects me," he added, "and two, for God's sakes, be honest with me." In the end, Nikki was correct -- Johnny and Rob were who he wanted for his best men -- but he wanted to be the one who told them the news.

Wedding Dress Shopping Gone Wrong

A woman trying on wedding dressed for the first time is supposed to be an exciting moment. This wasn't the case for Nikki.

"Finally, my sister is trying on wedding dresses!" Brie said to the camera. "I am so excited to be here 'cause Nicole has been dreaming about this moment forever, so hopefully we find the one."

Nikki was bummed out the entire time, however, as she tried on a collection of gorgeous wedding gowns.

"I thought you're supposed to be excited for this," she said. "Like when you watch the movies or all I'll hear from my friends is like, 'Oh my gosh, greatest day! Break out the champagne!' And like for me, there's just something that's not feeling right."

Engagement Party Pout

Wedding dress shopping was mild compared to the engagement party that followed. "Stuff is going to go wrong today, let’s just take it in stride," John said to Nikki before their engagement party kicked off. Little did he know how true those words would be.

"So the engagement party is here. I feel so overwhelmed," Nikki said in a confessional. "I honestly feel like I'm about to have an anxiety attack. I just feel like I'm on this roller coaster of emotions and I feel like I'm going to explode. It's just all too much for me."

"Does it make you realize, like, it's actually happening?" Cena asked Nikki during a heart to heart conversation. "Yeah," she admitted, "I just get so busy with everything else, I didn't even have an outfit for today."

"You can still back out if you want," Cena joked, to which Nikki responded, "I know, I have until 5/5 to do that." His reaction to that: "OK, can you maybe let me know on 5/4?"

As guest started to arrive, Nikki began to feel that she was forcing smiles. "I'm trying to be excited, but there is just a part that will not let me," she said. When she then surprised John with his two best men, she started feeling even more stressed.

"John literally is on cloud 9 right now, like he has his pep in his step and his permanent smile," she said. "I can see how happy he is, like his eyes are just twinkling like they’ve never twinkled before and that makes it so much harder on me that I’m feeling the way I am because I just don’t get why I’m feeling that was." She added she was happy to see him happy, though.

Baby, Baby, Baby

Brie Bella pulled a whoopsie by then convincing their brother J.J. and sister-in-law Lauren to announce that they were expecting their second child. That announcement pushed Nikki over the edge. "Woah, another person around me is having a baby. I’m done. I don't know," she explained in a confessional, as the camera showed her walking out of the party.

"I am so happy for my brother and his wife," she said. "It's just it's hard not to be affected when everyone around you is having, well not only one baby, they're having more. They're having families. I just, I just know deep down I want a baby. I just, I guess I don't know, I want to be a mom and I feel like I can't live the rest of my life not having one."

As she and John headed to Napa to put a downpayment down for the wedding venue, John knew something was wrong. Once they reached the location and found a bedroom to talk, Nikki finally let it all out.

"For some reason since [Brie's daughter] Birdie's been born and I've spent a lot time with Birdie, it's just brought up these feelings of really wanting to be a mom and I don't know if I would regret it later on in life if I wasn't," she told John through tears. "But I love you so much and I feel that's always been worth sacrificing for and I think just because we're getting married and everything's so permanent, that it's just, not that it's making me feel suffocated, but it's giving me just a bit of anxiety knowing like, okay the day 5/5 comes, that's it. Like, the mom thing's done."

After Nikki said she'd never "force" John to be a dad, he added, "I know, likewise. I would never force you not to be a mom. I don't even want to say it's a surprise, but I even told you so many times that this would happen."

That was when Cena dropped the bomb and said, "I'm not sure we should go through with this." The episode ended with a "To Be Continued ..."

We'll see what happens next when "Total Bellas" airs Sunday nights on E!

View Photos Getty John Cena, Nikki Bella and Apatow Clan Attend the 'Blockers' Premiere