'Teen Mom' Kailyn Lowry Names Her Newborn — 8 Weeks After His Birth!

At last! Kailyn Lowry has officially revealed the name she chose for her third child.

The Teen Mom 2 star made the big announcement Sunday on Instagram, sharing a photo of her 8-week-old son lying on top of a custom Highway 3 blanket with his name on it.

“Lux Russell, 08/05/17,” she captioned the sweet picture. “7 lbs. 15 oz., 19?” born at 3 a.m. on the dot. It only took us 7 weeks to decide a name and 8 weeks to make it official.”

Lowry, 25, announced she was expecting her third child on her blog in February, though she didn’t reveal the identity of the father until May, when she confirmed it is her longtime friend Chris Lopez.

Lowry and Lopez welcomed baby Lux on Aug. 5, and up until now, the MTV star has only referred to him as “Baby Lo.”

Lowry is already mother to son Isaac Elliot, 7, whom she shares with ex-boyfriend Jo Rivera, and son Lincoln Marshall, 3, whom she shares with ex-husband Javi Marroquin. She and Marroquin are set to star in the upcoming season of Marriage Boot Camp: Reality Stars.

As she adjusts to her new life as a mom of three, Lowry is finding her footing with Lopez, with whom she’s been “trying” to co-parent Lux with, she recently told PEOPLE. (Lowry also confirmed that Lopez “definitely won’t ever be on the show.”)

“It’s just kind of hard,” she said. “The dynamics are different between me and Chris, than with me and Javi or me and Jo. It’s a different kind of co-parenting.”

“Right now, Baby Lo is so new,” she added. “We’re trying to figure out what works for us.”

As for the possibility of having more children, Lowry revealed that she’d like to have a girl at some point.

“I’m open to more kids, but I’m not going to try right now,” she said. “Right now, I’m pretty good where I’m at. But, yeah, one day.”

Season 9 of Marriage Boot Camp: Reality Stars premieres Oct. 13 at 9 p.m. ET on WE tv.