Johnny revealed that he initially thought he was suffering from depression before learning that it was actually a malignant brain tumor.
"I'd even gone to the doctor and the doctor said, 'You know, all the symptoms seem like depression.'"
When he found out about his brain tumour, however, Johnny's neurosurgeon told him it was just the immense pressure on the brain.
"After having found the tumor, the neurosurgeon said, 'No, no it's not depression at all, it was because there was so much pressure put on your brain, it was causing all these different symptoms.'"
The star also revealed to Carrie that he wasn't sure how long the tumour had been growing.
"The surgeon said it could have been potentially growing from two to ten years," he said.
Johnny went on to reveal that his girlfriend, Tahnee Sims, was asked by doctors to sign off on his brain tumour operation, and she was told there was a 1/20 chance he wouldn't make it through.
If he hadn't gone in to hospital that evening with what he thought was a migraine, doctors said that he would have died that night with a brain aneurysm.
"It's sheer luck I went in when I did and everything happened the way it did or I wouldn't be here," he told Carrie.
We wish the star well as he continues his treatment, and we're sending all of our love.