Jana Kramer Says Anniversaries with Mike Caussin Make Her 'Very Uncomfortable' as They Hit 5 Years

After all the ups and downs they've faced throughout their marriage, Jana Kramer isn't going to sugarcoat things.

The country singer, 36, is celebrating five years of marriage with husband Mike Caussin, 33, on Friday, but Kramer is the first to admit their relationship is far from the fairy tale she dreamed of growing up.

"I never thought that we'd be here, to be totally honest," Kramer — who's releasing a relationship self-help book with Caussin in September called The Good Fight — tells PEOPLE exclusively. "The last five years has been just a lot of freakin' work, and I truly hope the next five will be easier because of the tools that we have."

While most couples publicly mark their anniversaries with over the top social media posts, "I can't go onto my Instagram — or basically our Instagram — and say 'Happy five year anniversary ... it's been the best marriage ever!" says Kramer, who has daughter Jolie, 4, and son Jace, 17 months, with Caussin. "I get very uncomfortable whenever anniversaries come up and have to post about it."

Over the years, the Whine Down podcast co-hosts have been candid about Caussin's infidelity and struggle with sex addiction, but Kramer acknowledges it's a two-way street.

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"There are things I could have done better, things he could have done better. For both of us it's been really hard," she says. "But we're still fighting the good fight, and I think that's the most honest, authentic [message] to put out there at five years. I could say we worked really hard to get here."

As they look ahead to their future, Caussin says he feels grateful for his wife's resilience.

Courtesy of Jana Kramer and Mike Caussin Jana Kramer and Mike Caussin with Jace

"Ultimately, we wouldn't be here if it wasn't for Jana. I've given her many reasons — not just from the beginning, but throughout our relationship — that no one would blame her or fault her for walking away," he says.

Still, Kramer credits Caussin for choosing to fight for their marriage as well.

"I was not nice to him at times. I said some mean stuff to him, like nasty things," she admits. "He could have been like, 'Screw this. I don't need this.' To be in his situation to stand there and just try to be empathetic has got to be really hard for him too."