Hollie Sharman was utterly convinced she was dying. The 25-year-old would show up at the hospital "four to five times a week" complaining of excruciating chest pain, and one particularly memorable visit saw her spend 13 hours in A&E. Doctors ran test after test and found precisely nothing wrong. Which, as it turns out, was the problem.

Sharman says she had "always worried" about her health as a child, recalling how she'd make "any excuse" to get sent home from school so she could crawl into bed. Her 22nd birthday meal was spent in the restaurant toilets "having the worst panic attack I've ever had" - a milestone that kicked off years of health anxiety, hours of symptom-searching, and a general sense of panicked isolation.

"I was constantly Googling and using ChatGPT, every source I could get that could tell me what was wrong," she says. Because nothing says peace of mind like asking a large language model to diagnose you. "I spent so long in the hospital. They'd tell me it's nothing, they'd check everything. I'd go home, but then my legs would feel weak, so I'd Google that and then it would say it's a sign of heart failure. So I'd go back, it was literally a constant cycle."

At its worst, she "completely disconnected from everyone" and stopped replying to family messages to avoid repetitive conversations. Her relationship took a hit too. "It got to the point that nothing he said would be the right thing," she says. "I would get upset because he didn't understand what was going on inside my own head. How can you tell someone everything's fine when I think I'm actually dying?"

Clinical psychologist Dr Kirren Schnack defines health anxiety as "a constant worry about being seriously ill or becoming seriously ill when you are not." Key signs include "checking" behaviours - frequently examining your body, taking your temperature or blood pressure, or researching symptoms online. Another is constantly seeking reassurance from the internet, friends or family that you're safe and healthy, she tells Complex with Kimberley Wilson. Others may experience "avoidance" - not looking at their body or skipping doctor's appointments because they fear "the worst." Some may "take on the persona of somebody who has an illness," she adds. "You may slow down your movements and stop exercising, you're treating yourself and your body and mind as if you are already ill."

Sharman was eventually diagnosed with health anxiety and health-related obsessive compulsive disorder (OCD). She credits her family and partner with being "incredibly supportive" and helping her reach a "better place" with anxiety-management techniques. One trick: writing down her symptoms - "chest pain, excruciating" - and then noting at the end of the day that she was fine. "And then next time I'd have it, I'd have something to read and I'd be like, but I thought I was dying then and I wasn't."

Sharman says her health anxiety "doesn't control her life any more." Her advice: "You need to push yourself and do things when you're anxious, don't put your life on hold because I did for so many years."

Dr Schnack says if you have a symptom that is "new, concerning or doesn't go away," it's "responsible health behaviour" to check the NHS website. If a symptom persists beyond two weeks, she advises making a GP appointment. (Here's when to call 111, 999 or go to A&E.) And here are some tips from Dr Schnack that might help:

Challenge worst-case thinking - give your brain other explanations for physical sensations; a stiff back might be poor posture rather than a serious illness.

Limit reassurance-seeking - set rules and time limits on how often you ask friends or family about symptoms, and stick to them.

Burn off anxious energy - take quick bursts of movement, like jumping jacks, to help process adrenaline and cortisol.

Ground yourself - use strong sensory experiences such as holding an ice cube or tasting something sour or spicy.

Breathing techniques - take a long breath through your nose, add a second inhale at the top and release it with a long sigh through your mouth.