Imagine this scenario: you're woken in the night by chest pain. When you get up the next morning to do the kids' breakfast your legs are like lead, your vision is blurred and when your seven-year-old asks for Coco Pops your brain reacts as though they've asked you for the cubic volume of the moon.
Suddenly you can't stand up any more and everything around you disconnects. You are alone with the kids and you can't get yourself to a doctor. Would you call a cab or an ambulance to take you to A&E?
I wouldn't call either, because I know there's no point. I have the illness known as M.E. or Chronic Fatigue Syndrome. This scenario is a regular occurrence for me when I have a flare up. Yet even when I've been taken to A&E, unable to move or speak, doctors draw a blank as to what's going on inside my body. I get sent home with a paracetamol and a pat on the head, if I'm lucky.
M.E. is so poorly understood that doctors can't even agree on its name. It stands for Myalgic Encephalomyelitis, but the medical establishment prefers the term Chronic Fatigue Syndrome. There is no test for it, let alone a cure, and it affects about 250,000 people in the UK.
The reason we sufferers hate the term Chronic Fatigue Syndrome (or CFS) is because the name is like a whitewash. People are disabled by M.E. to the point of losing the ability to walk, drive or read a newspaper - even to the point of needing tube feeding. But the label CFS implies we are just "tired".
As my lovely friend M confessed to me the other day, after five years of our daughters being best friends: "It's hard to understand you guys with M.E. because when you say you're tired, it's like, 'well we get tired too'."
Welcome to planet parent. How many other mums I know are thinking the same thing?
So what's it really like to live with M.E.? Well, think of your mobile phone, which probably runs out of charge by the end of the day. People with M.E. are like mobile phones with knackered batteries that only charge up to about 10, 20 or 30 percent. After the equivalent of sending a couple of texts and checking the weather app our battery dies and we crash. That could be simply having a shower and getting dressed.
Friends see me walking my girls to school and smiling at the school gates, but what they can't see is that the school run uses up about 60% of my energy charge for the whole day. Do the maths, and that doesn't leave much for doing the dinner, the homework, the bedtime, the washing and the pre-teen dramas that command my daughters' full attention.
I hate having to explain that I have a disability that prevents me taking my girls to Brownies after school, joining the camping weekend, pitching in with the school fair or helping friends out when they're stuck for childcare - because for that snapshot in the day they see me looking entirely "normal".
And I'm one of the lucky ones. My disability may be invisible, but the really invisible people with M.E. are those you never even see or hear about, because they are confined to a bed in a darkened room for years and sometimes decades at a time.
Every time I feel sorry for myself because I'm a disabled single parent I think of Jenny, and others like her. At 29, beautiful, talented Jenny longs for her first kiss and the chance to be outdoors with her friends, because a very severe form of M.E. has cruelly stolen her youth from her. M.E. doesn't usually kill, but it can take your life away.
When I was 23 my M.E. was as bad as Jenny's. My 'battery' wouldn't charge at all, leaving me virtually paralysed and intolerant to all sensory stimulation. I couldn't sit up, feed myself, hold a conversation or even listen to the radio. My mum and dad had to care for me as you would a newborn baby. I inexplicably recovered. Today I am 'only' moderately ill, whereas Jenny has remained in this state (which you can barely call living) for the past 12 years.
Every time I get down about all the things I can't do with my girls – take them to the park, sometimes even read them a bedtime story – I remember there are others who would give their right arm to have even the halfway recovery that I've had. And the miraculous fact that I've had children at all chokes me up inside.
So next time someone tells you they have M.E., take it as a compliment that they've even shared this information with you. Assume nothing from their appearance about their day to day life. Don't tell them about how you get tired too. Above all, remember: for every person you encounter with M.E., there's another one who has disappeared from view.