Olivia Munn had an "unbelievably difficult" time with postpartum anxiety

Speaking on 'The Kelly Clarkson Show', she said: "I had heard about postpartum depression and I was prepared for it, but postpartum anxiety was something I had never heard about and it hit me like the entire ocean was on top of me.

"It was unbelievably difficult. It was a month after I had the baby and all of a sudden at four a.m., my eyes just pop open, and I start [gasping for breath] and then my chest is tight and it stays tight all the long.

"For a whole year, every day at four a.m my eyes would pop open and I would be gasping for air and my chest would stay tight all day long. It was like this constant anxiety, a panic. If you're holding your breath underwater, and you can't come up for water, imagine what that feels like. I felt like that every single day."

The 'Newsroom' star has since learned that her "low milk supply" could have played a part in her condition and is "heartbroken" for women who experience feelings of negativity towards their baby, but her ordeal came directly before she learned that she had breast cancer.

She added: "I only learned this later, but I had a really low milk supply and apparently when you stop breastfeeding and you stop producing milk, your hormones drop and that could've been a contributing factor to my postpartum anxiety.

"But for women who deal with postpartum anxiety, especially the women who have thoughts of self-harm and negative thoughts towards their baby, my heart just completely breaks for them. If I had known about it, I would've prepared for it. "I was postpartum for a long time and I got out of that. Just a few months out of that, I found out I had breast cancer."

Olivia's diagnosis resulted in four surgeries, a double mastectomy, and medically induced menopause, but she insisted that keeping the news away from her fans meant she could battle the disease without any "noise" and could recover in peace.

She wrote on Instagram: "Keeping it private for as long as I did allowed me time to fight without any outside noise at all."

Olivia previously explained that she had been for her usual mammogram and her cancer would have gone unnoticed until her next routine appointment but her doctor decided to do a simple risk assessment test based on factors such as her age, medical history and the fact that she had her first child over the age of 30.

After finding that she held an almost 40 percent chance of developing cancer within her lifetime, O livia went for an MRI which led to further tests confirming the disease.