It's an illness which affects one in 20 people yet, even now, fibromyalgia is not fully understood. The classic symptoms are muscle and joint pain along with fatigue - however, even medical experts disagree on its diagnosis.
For sufferers, though, it means constant pain,exhaustion, and depression - and the condition is becoming more and more common among young people.
Now, a national campaign has been launched to raise awareness. Cary Johnston has been to see a woman from Lambourn who is determined to remain positive, despite her condition.
interviewees: Lucy Pickup, fibromyalgia campaigner; Dr Deepak Ravindran, Royal Berkshire Hospital; and Andrew Sharp, Healthwatch, West Berkshire.
For details about the condition and how it can be treated, click here.