Talk of baby number 4?

So, my fiance and I have been talking about having another baby. We are a blended family, he has one child from his first relationship who is 14, I have one child from my last relationship, she's 7 and we just had a baby together in November she is 3 months old. I just want some feed back from other mom's. Is it true that having 3 kids around the clock is extreme chaos? We are both 33 and dont want to wait longer than a year before we start trying again.