How Flip or Flop Star Tarek El Moussa’s Mental and Physical Health Battles Led to Divorce: ‘I Was So Miserable’

The last three years haven’t been easy for Tarek El Moussa.

“I went through hell,” the Flip or Flop star says of battling thyroid and testicular cancer and suffering through a debilitating back injury in the short time since he first found fame on his hit HGTV show.

In the current issue of PEOPLE, the reality star, 36, reflects on how those physical health battles led to an emotional turmoil which took a toll on his 7-year marriage to his costar Christina.

“We used to be so energetic,” Tarek says in the magazine of his relationship with his wife, whom he secretly separated from after a shocking incident involving a gun last May. “But with the businesses and the cameras and the cancers and the surgeries and my back, we started losing that energy. That’s what led us to where we are.”

Tarek says being diagnosed with both thyroid and testicular cancer was “devastating” at the thought that he was going to die, but the worst part was the “aftermath” that came post-surgery and post-iodine radiation treatment.

“I became very emotional,” says the Realtor, whose hormone levels were “all over the place” after treatment. “I was stressed and anxious and exhausted.”

The medication he was prescribed after his surgeries caused his heart to palpitate, so he began wearing a heart monitor because he feared he’d have a heart attack. His stress compounded when he threw out his back playing golf in 2014, at the same time Christina was enduring an intense round of IVF and doctor-ordered bed rest following a miscarriage.

“Those were the worst months of my life,” says El Moussa, who gained 40 lbs. because of his hormone imbalance post-surgery. While immobilized by his back injury, the 6-ft.-tall reality star then lost almost 70 lbs.

For more from Tarek El Moussa — including how his 6-year-old daughter is coping with the divorce — pick up the latest issue of PEOPLE, on newsstands Friday

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“I looked like death,” he says of the rapid weight loss. “I wasn’t the happy, outgoing guy I once was. I was so miserable. It was a struggle just to wake up in the morning.”

That struggle seriously impacted his marriage to Christina, who told People shortly after their son’s birth that she felt “overwhelmed” with two young kids, an ailing husband and a work schedule that never let up.

“We lived through a lifetime of setbacks in a short period,” Tarek says now. “And we were so busy, we never slowed down to be present with each other and talk about things that were bothering us.”

After attending therapy, the El Moussas ultimately decided to split and Tarek began making a new life for himself in Newport Beach, which is 30 miles from his family’s home in Yorba Linda, Calif.

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Spending time with his daughter Taylor, 6, and son Brayden, 18 months — whom he splits custody of “about 50-50” with Christina — remains his favorite way to spend his days, but Tarek is also taking advantage of alone time to work on himself.

“I realized I was tired of feeling the way that I felt,” he says. “I decided to do whatever it took to make sure I got to where I was before all my medical issues.”

After working with his doctors to find a combination of hormone medications that would least impact his mood and energy, Tarek says “my meds are where they need to be.” He’s also working out regularly and is back to his “healthy” weight of 195 lbs.

“When you’re going through something like I did, you don’t realize how bad it is until you get out of it,” Tarek adds. “But now I’m happy, healthy and dedicated to what makes me the happiest: being the best father possible. Everything’s perfect.”