"I had such a wonderful, energetic pregnancy," Teigen writes. "Luna sat inside me like a little cross-legged Buddha facing toward my back for nine months. ... John (Legend, her husband), my mom, and my

sister were all in the delivery room. John was DJ-ing. Luna, fittingly, popped out to the song 'Superfly.' The first lyric is 'Darkest of night. With the moon shining bright.' I immediately

put her on my chest. ... I was so happy. And exhausted."

Teigen, Legend, and baby Luna lived in a rental home and a hotel after Luna was born because their home was under construction. It was then when Teigen's symptoms first began to emerge.

"I blamed whatever

stress or detachment or sadness I was feeling at that time on the fact that there were so many odd circumstances," she says. "I remember thinking: 'Maybe I’ll feel better when

we have a home.' "

But things didn't get better. Teigen started to experience excruciating lower-back, shoulder, and wrist pain, and couldn't get out of bed most days. Most alarmingly, she couldn't eat.

"I would

go two days without a bite of food, and you know how big of a deal food is for me," the bestselling cookbook author says in her open letter. 

If

she didn't have to go to work or an event, Teigen never left her home, she admits.

"I mean, never. Not even a tiptoe outside," she says. "I’d ask people who came inside

why they were wet. Was it raining? How would I know — I had every shade closed. Most days were spent on the exact same spot on the couch and

rarely would I muster up the energy to make it upstairs for bed."

She says Legend would do everything he could to make her feel better, even sleeping on the couch with her — "sometimes four nights in a row."

At first, Teigen chalked

her mood changes up to the stresses of being a new mom.

"Maybe I’m just not a goofy person anymore," she thought to herself. "Maybe I’m just supposed to be a

mom."

But soon her symptoms became too prominent to ignore: She had to go to the hospital because of her back pain — "my bones hurt to the core," she explains

— and she couldn't work on her second cookbook, because "the idea of having to test and taste recipes actually made me vomit."

This past December, Teigen saw her doctor and was officially diagnosed with postpartum depression and anxiety.

"I remember being so exhausted but happy to know that we could finally get on the

path of getting better," Teigen says. "John had that same excitement."

She started taking an antidepressant, and began sharing her diagnosis with those close to her.

"I felt like everyone deserved

an explanation, and I didn’t know how else to say it other than the only way I know: just saying it. It got easier and easier to say it aloud

every time," she admits.

Now, she's sharing her news with the rest of the world to give postpartum depression a familiar face — and let other women know that they don't have to suffer in silence.

"I

look around every day and I don’t know how people do it," Teigen says. "I’ve never had more respect for mothers, especially mothers with postpartum depression. ... I don't want people to have

it to feel embarrassed or to feel alone. I also don't want to pretend like I know everything about postpartum depression, because it can be different for everybody. 

"But one

thing I do know is that — for me — just merely being open about it helps."

You can read Teigen's entire essay over at Glamour.