B.H.
I've had 4 children and started showing a bit earlier with each successive pregnancy. Everything is looser inside so it's common to show earlier than with a previous one. Like you, I was several weeks along before realizing I was pregnant - it's easy to miss the signs when you a busy chasing little people all day.
Good luck with the new little one! It's so much fun having oodles of little ones in the house!!