Simpson and fiancé Eric Johnson welcomed the little guy via a planned C-section on June 30. The couple also has a 15-month-old daughter, Maxwell.
"With two kids, we have our hands full, but every day is a new adventure," the 33-year-old told the mag. "It's fun! I feel very at peace with being a mom."
The singer added that she may be done having kids."Pregnancy is a lot. It was hard to do two so close together. I have this huge sense of accomplishment, and I feel in my heart that I'm done. But obviously, accidents do happen!"
Check out the full story in the September 9 issue of Us Weekly.