“Fatherhood is the greatest job in the world” forNick Lachey— but he’ll be the first to tell you “it isn’t the easiest.”

In the photo’s caption, Lachey, 45, shared his entry in the “#UnspokenStories” hashtag trend, revealing, “As I tell my kids everyday, my number one job is to protect them. Never did I feel more helpless and unable to do my job than when my son Phoenix was born.”

“I felt a vulnerability I had never known before and a fear I wasn’t familiar with,” Lachey continued. “I can only imagine how many fathers out there felt the same way I did in that moment.”

Nick Lachey/ Instagram

Nick Lachey and Baby

“Now, 2 and a half years later, those weeks seem like an eternity ago as I watch my happy, healthy toddler run and climb and play,” Lachey added gratefully. “AsDads, I think we often feel a pressureto be this impenetrable pillar of strength. Phoenix reminded me that the ultimate show of strength is love.”

RELATED VIDEO: Vanessa Lachey Breaks Down as She Reveals She Underwent an Emergency Surgery During Premature Birth of Son Phoenix

The couple have been candid about the harrowing experience of Phoenix’s premature birth following an umbilical-cord prolapse and his subsequent hospitalization overrespiratory syncytial virus (RSV), which Vanessa recently revealed was the most challenging part of her life and marriage — and is something she has not yet gotten over.

But as parents to Phoenix, 4-year-old daughterBrooklyn Elisabethand sonCamden John, 6½, Vanessa and her husband soon figured out how to balance parenting duties during the hospitalization — though it wasn’t easy.

“[It was] definitely the hardest part in my life and also in my marriage,” theTop Chef Jr.host said during a May interview forMom2Mom. “Not in a negative way, just in a very challenging way.”

“Nick actually mentioned the other day, ‘I don’t know if we’ve ever gotten over that.’ We’ve never reallytalked about it and gotten over it. We’ve still kind of just been playing catch-up since then, you know?” she revealed. “It’s an intense time.”

source: people.com