My REM sleep debt is mounting up. It's two months since Max was born and I haven't yet had a snooze longer than two hours.

Just as my dreams start to get interesting I'm woken up by a hungry wail.

This is the bit I'd forgotten about with new babies. You see others with their offspring asleep in car seats and buggies and you think, ahh, how sweet and peaceful.

And you read in the books that infants sleep for up to 18 hours a day which must mean you can squeeze in your own eight hours and still have time to do other things.

But the reality is the quality of my sleep is so poor that, even when he's asleep and I'm awake, my brain has lost its ability to function.

For example, it's taking me twice as long each week to write this column. My first attempt is utter gibberish and the second, well, I'll let you be the judge of that.

In conversation I'm, at best, monosyllabic. Any question more complicated than "How are you?" makes me flummoxed.

My husband wanted to know what toppings I wanted on the pizza he was making the other day and had to interpret my selection from my actions: A smile for cheese and an 'O' shape with my mouth for olives.

Our four-year-old, who hasn't yet let me catch up on the sleep deprivation she caused during the first two years of her life, has no sympathy for a tired mother.

"Make up a story, Mummy," she says, presenting me with a selection of half-dressed Barbies.

So I start giving her the old Cinderella one and she gets cross and interrupts, telling me this one is going to be different.

The prince is marrying the horrible stepmother and the ugly sisters are going to be turned into mermaids. Each time I, wearily, try to reach a happy ending, she changes the plot again.

What I want to do mostly is lie down on a bed and close my eyes until September. As this option isn't available to me, I try the alternative, which is to eat.

In fact, if I wasn't feeling so tired all the time, I would be far more worried about the fact I haven't lost the weight I gained in pregnancy to slip into my Liz Hurley-style Versaces (I wish!).

I'm out of maternity clothes but I'm not yet back into the size 12s, which now look ridiculously small.

Did I ever really have a 26in waist? All right, so that was ten years ago but I did have some sort of foolish notion that childbearing didn't necessarily mean I'd end up looking so mumsy.

As I can't cut down on the food (at least I have the excuse I'm breastfeeding), I have attempted some exercise.

I started this week by having a swim with my four-year-old while my husband minded the baby for 40 minutes. It was bliss until I caught sight of myself in the changing-room mirror.

I've also bought a book on post-natal yoga. The only exercise I've attempted so far involves breathing in through one nostril and out through the other - or something like that.

It's made me feel more relaxed although it's not made a blind bit of difference to my midriff yet.