Sometimes the pain would shoot through her chest without warning — a sharp, debilitating burn so excruciating that Kerisha Mark was convinced she was having a heart attack.

Other times, it started in her shoulders before crawling up the nerves in her neck and settling inside her head, where it would blossom into a full-blown migraine that could last for days.

Each time Mark ended up in the emergency room, doctors told the 40-year-old high school social worker from Beaumont, Tex., the same thing: She wasn't having a heart attack and, no, she didn't have a brain tumor, either.

The problem was her breasts.

More specifically, their size. Mark had always had an exceptionally large bust, she said, but by her late 30s, her chest had ballooned to size 36NNN due to a rare hormonal condition called gigantomastia.

The condition, which results in the massive enlargement of breast tissue, can occur during puberty or pregnancy. Gigantomastia can also unleash a spate of health issues that quickly begin to take their toll; for Mark, they included pulled muscles in her chest, severe back pain and emotional distress.

"I could not run or jump or work out at all," she told The Post. "I was very limited in a lot of things I could do. I mean, you can't find a sports bra that size anyway."

Mark estimates that her breasts weighed around 15 pounds each and said that she began using duct tape to hold them in place.

After several years of reluctantly considering surgery, Mark decided to get a breast reduction from Franklin Rose, a well-known plastic surgeon based in Houston. Rose told The Post that he couldn't recall seeing a patient with larger breasts in almost 35 years of work as a plastic surgeon.

"The breasts really hung down to her hips and were essentially like carrying around three basketballs at all times because they were so large," he said. "When we went into the exam room — I don't know if I would use this word 'shocking,' but it was certainly startling to see breasts of that magnitude."

Fortunately, Rose said, breast reduction surgery is largely the same regardless of the patient's breast size, though he was forced to bring in a second assistant to facilitate the four-hour surgery in September, just days after Mark's 40th birthday. During the procedure, Rose said, he removed 15 pounds of tissue.

"The challenge is not so much what you remove, but what you leave behind to make a pretty breast," Rose said. "We left her with a nice full DD that she was very happy with."

Left untreated, he added, Mark may have developed degenerative kyphosis, a condition in which a person's spine curves forward, forming a hump or "hunchback."

More than a month after her surgery — which, she said, was covered by insurance — Mark said she's feeling much better and that her symptoms have disappeared. In addition to losing weight from her breast reduction, she's dropped another 10 pounds in recent weeks.

She plans to start exercising again. She is also picking out a new wardrobe, she said, and is excited about purchasing her first bathing suit in two decades.

"Getting my breasts reduced was like a divorce," she said. "And like a bad relationship, you don't always realize how bad things were until it's over."