Excerpt from Sarah Metcalfe’s (from York, UK) Open Letter that seems to sum it up well for me:

I know I may not look ill, in fact I choose to smile rather than cry, but I do suffer from a long term condition that causes pain and fatigue all over my body and these symptoms are:

increased sensitivity to pain
fatigue (extreme tiredness)
muscle stiffness
difficulty sleeping
problems with mental processes (known as “fibro-fog”) – such as problems with memory and concentration headaches
irritable bowel syndrome (IBS) – a digestive condition that causes * stomach pain and bloating
dizziness and clumsiness
feeling too hot or too cold – this is because you’re not able to regulate your body temperature properly
restless legs syndrome (an overwhelming urge to move your legs)
tingling, numbness, prickling or burning sensations in your hands and feet (paraesthesia)
anxiety and depression