The songstress was just seen earlier this week on a back-to-school picnic with her ex Jordan Bratman and their son, Max.
So just how is Xtina losing the baby weight in such a short amount of time?!
"Christina was very healthy throughout her pregnancy and is continuing it now after the baby," a source tells E! News.
"She is very dedicated to yoga. So much that she has never stopped practicing it. She did yoga the entire time she was pregnant. And Christina has already been working hard on getting her bod back in shape! She is doing private yoga sessions and loves how it makes her feel."
Aguilera apparently "loves the way it makes her look and feel, inside and out. It's so calming and keeps her centered. She is obsessed!"
And aside from breastfeeding her baby girl, she's "eating clean and watching her portions."
Our insider adds, "Everything is about moderation. She will have cheat meals occasionally too. Running after Max also is helping her burn some extra calories. There's never a quiet moment, Max is very active!"
Speaking of the singer's son, we're told that "Max is being a very helpful big brother" and "loves having a little sister."
Understandably, Christina is "all about family right now, that's what her priority is."