"It's been a roller coaster, but all good," Lachey, 38, said. "It's been incredible to go through for the first time. It's all kind of surreal. Every day is a new surprise or expression. It's a lot of fun. I try to do everything with the baby. I sing to him. I shush him a lot. It's all about spending as much as you can."
And he has taken the advice he received from his brother, Drew Lachey, father of two, to heart.
"My brother said smell the baby a lot. That smell of your newborn baby doesn't last very long but it's something you'll always remember," he explained. "So I find myself sniffing his head and his neck. There is that baby smell that is so special, especially when it's your own baby!"
Lache -- who said he has been working in the studio on a lullaby project "inspired" by his baby boy -- has also been bonding with his son over football.
"Now with Camden, he has his own Bengals onesie and the team is 3-1 with him cheering them," the proud dad gushed. "So in the last month, my tradition has been changing him and getting him ready for football at 10 o'clock. Then we sit together and watch. It's awesome."