Kody Brown is still living in the shock of his son Garrison’s sudden death.

The Sister Wives star’s son was found dead after an apparent suicide on March 5, and Kody tells PEOPLE it “still feels like a shock.”

“The hard part is giving away that future that I saw for him, the excitement,” Kody, 55, says. “It’s strange having your child pass. The wave of grief is different that any wave of grief I have ever had with a best friend passing, with a relative passing. It’s different. And it is different in the idea that it’s irreconcilable — the future that we missed with him.”

Kody admits that his relationship with his son — one of his 18 kids who he shares with ex-wives Christine, Meri and Janelle Brown and current wife Robyn Brown — “certainly could have been better” before Garrion’s death six months ago.

“We could have been talking more. I’d get texts, stuff like that, and we could have, retrospectively, we could have done so much more,” he said. “And it was almost like — I’m busy with my life, he’s busy with his life, and when we connect, we’ll connect.”

“It was kind of like, we’ve got forever. It was more like it was a convenience of time that I felt like I had,” he added. “Retrospectively, there would’ve been more of a regular catching up and touching base.”

Garrison’s death has changed Kody “irrevocably,” he says. “I can’t get back to where I was. I can’t reconcile that he’s not here.”

“You do have a little bit of an expectation — and especially with somebody who’s got essentially a bright future. He was planning a future. He always wanted a story to tell, some adventure. He was always either cracking a joke or wanting to talk about an adventure,” he recalls of the 25-year-old.

Kody’s “only regret” when he thinks back is that he wishes he’d taken “advantage of the time” he had with Garrison, one of the six kids he shares with Janelle, 55.

“I want to go out to dinner again. I want to sit down. I want to have a beer. I want him to try and make me laugh because he was kind of that way. The only regret is just, gosh, I would just do that more often,” he says. “The only regret is that you didn’t do something. You didn’t take more time.”