Chrissy Teigen shares emotional post about late son Jack

Chrissy Teigen is reflecting on the loss of her unborn son, Jack, whom she would have given birth to this week, ahead of undergoing surgery for endometriosis.

Teigen took to Twitter on Wednesday to tell her followers that her "little jack" would have been born this week. Given the timing, the 35-year-old said she is understandably "a bit off."

"I truly feel kicks in my belly, but it's not phantom," the "Cravings" author continued. "I have surgery for endometriosis tomorrow ... but the period feeling this month is exactly like baby kicks."

Endometriosis, a medical condition where tissue similar to that which normally lines the inside of the uterus grows outside of the uterus, may affect more than 11% of American women between the ages of 15 and 44, according to the U.S. Department of Health and Human Services Office on Women's Health.

In another tweet, the "Lip Sync Battle" host shared a video of her belly and it appearing to react as if a baby were kicking inside the womb.

"I'll pretend it's him saying hi -- it never stops," she added.

Teigen first revealed she was pregnant with her third child with husband John Legend in August via a music video for Legend's song "Wild."

In September, Teigen suffered a pregnancy loss after being admitted to the hospital due to "excessive bleeding." Prior to her hospitalization, she had been on weeks of bed rest.

"We are shocked and in the kind of deep pain you only hear about, the kind of pain we've never felt before," Teigen shared at the time in a heartbreaking Instagram post. "We are so grateful for the life we have, for our wonderful babies Luna and Miles, for all the amazing things we've been able to experience."

"But everyday can't be full of sunshine," she continued. "On this darkest of days, we will grieve, we will cry our eyes out. But we will hug and love each other harder and get through it."

In October, the model opened up about losing Jack in an emotional personal essay.

"I definitely give myself permission to feel complete and utter grief," Teigen told "Good Morning America" in November. "Every day is so different. So when people ask me how I'm doing I always say I'm OK -- today."

Teigen and Legend, who have been married since 2013, have two children: daughter Luna, 4, and son Miles, 2.