Health anxiety is a mental illness which is similar to anxiety, except it's focused on health. For example, you might randomly have a itch U need to scratch. A normal person wouldn't think much about if, but someone with health anxiety might think they have every single type of cancer and that they're gonna die cuz of it.
Guy 1:OH GOD, I CAN FEEL MY HEARTBEAT I THINK I'M HAVING A HEART ATTACK
Guy 2: Dude, everyone can feel their heartbeat especially if you focus on it. It's just health anxiety.